Type of polymict impact breccia identified at Ries crater in Germany; clasts are
25 cm - 50
m, subdivided
from allocthonous blocks (>50 m) by size, flow-emplaced instead of ballistically
like suevite
Go To Top
- CAI
- Calcium, Aluminum-rich Inclusion;
abundant in CV, and to a lesser extent CM, chondrites
- calcite
(also calcium carbonate)
- CaCO3; (terrestrial) alteration
product; very distict in optical: third order birefringence, greens &
pinks, often twinned;
polymorphic with aragonite.
- carbonaceous chondrite
- type of chondrite;
very similar in composition to the Sun, less volatiles; similar spectral properties
to type C asteroids
- Carlsbad twinning
- parallel
twin; twin axis [001] (z axis); composition plane (hk0),
usually (010); simple repetition; in both monoclinic & triclinic feldspars,
usually only 2 individuals, sometimes up to 6 [DHZ
294, pic]; common in orthoclase, may be present in plagioclase [Kerr
292]
- carotenoid
-
a class of red, orange, purple, and yellow
pigments occurring widely in nature, synthesized in plants, and
characterized by their solubility in fats; they are referred to as
lipochromes
when concentrated in animal fat. (Harcourt)
- cataclastic
- textural description; a breccia of powdered rock formed by crushing and shearing
during tectonic movements; characterized by granular,
fragmentary, or strained
crystals
- chadacryst
- crystal enclosed in
another crystal (the oikocryst) in a poikilitic
texture; usually euhedral; or crystal foreign to rest of the (igneous) rock
in which it occurs [see xenocryst]
- chassignite
-
one of a class of Martian (probably) meteorites; Chassigny is the only
known member of this class; dunite. See also sherggotites and nakhlites.
- chevkinite
-
(Ca,Ce,Th)4(Fe+2,Mg)2(Ti,Fe+3)3Si4O22, a reddish brown to black opaque,
brittle, monoclinic mineral occurring as irregular masses and prismatic
crystals, having a specific gravity of 4.3 to 4.67 and a hardness of 5 to 6 on
the Mohs scale; found in pumice fragments and ash from Cenozoic volcanism in
the western United States; dimorphous with perrierite
- chloritize
- to introduce a
chlorite radical into a compound
- chondrite
- A relatively
abundant type of stone meteorite characterized by the presence of chondrules; also implies Solar composition (minus volatiles)
- chondrules
-
Millimeter-sized glass spheres found in abundance in chondrite meteorites;
existed independently prior to incorporation in meteorite; shows evidence of
melting
- chromite
- oxide, part of
spinel group [DHZ, 424]
- clay
- One of a member of a large group of hydrous silicate minerals. Formed by chemical weathering of igneous and metamorphic rocks.
Type of clay formed is a function of the parent rock type and specific weathering
conditions. E.g., a basic igneous rock with high Mg content, subjected
to poor drainage and low rainfall (Mg remains in rock), will
produce montmorillonite. Whereas the same rock
subjected to high rainfall and good drainage (removing the Mg
from the rock) will produce kaolinite. One type of
clay can be produced first, and later weathered to another type of clay.
Clay minerals include kaolinite,
smectite, montmorillonite, illite, halloysite, saponite, allophane.
- clino-
- monoclinic version
of a mineral ??? [as opposed to ortho-]; literal meaning:
sloping, inclined
- clinoptilolite
- type of zeolite, common alteration product of more silicic glasses
- clinopyroxene
- any
monoclinic pyroxene, such as diopside, clinoferrosilite,
augite, or jadeite; high birefringence compared to orthopyroxene
- closure temperature
-
"temperature at which the observed or site partitioning of Fe and Mg is in
equilibrium" [Ganguly et al. 1997]
- cohenite
- (Fe,Ni)3C;
carbide, accessory mineral found in some iron meteorites
- colloform
- describing the
spherical texture of a mineral deposit resulting from colloidal
precipitation
- colloid
- a substance consisting
of very tiny particles that are usually between 1 nanometer and 1000 nanometers
in diameter and that are suspended in a continuous medium, such as a liquid, a
solid, or a gaseous substance
- comminution
-
the breaking down of material into a very fine powder [Penguin]
- complex twins
- if A &
B are normal twins and B & C are parallel twins, then A & C are complex
twins; B may or may not be present.
twin axis lies in composition plane & is normal
to a possible crystal edge
[see also normal twins, parallel
twins]
- composition plane
- - twin individuals meet
along this plane; usually the same as the twinning plane
[see twinning]
- compressibility
- - parameter that describes change
in volume per unit change in pressure of a meterial; β = -ΔV /
VΔP; or β = -1/v ∂v/∂P; compressability of water is
.0000034 lb/ft2; reciprocal of bulk modulus
- conformable
- - describing continuous
sequence of rock layers formed in parallel order without interruption; or the
contact between such layers; contrast unconformable
- consertal
- - ???
- cryptocrystalline
- - crystals are too small to
be distinguished under an ordinary microscope;
contrast microcrystalline.
- crystal settling
- - Gravitational sinking of
crystals from the liquid in which they formed, by virtue of their greater
density; A type of igneous differentiation
- cumulate
- An igneous rock
that forms by crystal settling
- cumulophyric
- see glomerophyric
Go To Top
- dendritic
- texture like a plant, in slender divergent
branches, branching, tree-like morphology.
- devitrification
- process
by which glass (re)crystallizes; crystals which form are spherical, radiating,
sometimes dendritic; most glass older than ~100 Ma has devitrified.
- diabase
- an intrusive,
medium-grained, basaltic rock consisting principally of labradorite
and pyroxene, ophitic texture is characteristic; commonly found
in dikes and sills; coarser-grained than basalt; (also dolerite)
- diagenesis
- The process of
chemical and physical change in deposited sediment during its conversion to
rock; also refers to processes somewhere along the continuum between
weathering (low-temperature processes) and metamorphism (high-temperature,
high-pressure processes), processes which can include compaction, dissolution,
cementation by precipitated minerals, and recrystallization.
- diaplectic glass
- glass formed by transformation of
a mineral to an amorphous phase due to a pressure release; resultant glass has
same composition as original mineral phase, but a lower density; differs in
physical properties from glass quenched from a melt under normal conditions
[Stöffler 1971]; e.g. maskelynite; disordered glass-like
substance formed by shock metamorphism, without melting (solid-state reaction)
- diastem
- a relatively short interruption in sedimentation with little or no
erosion occurring before deposition is resumed
- diogenite
- class of achondritic meteorite, consists
primarily of Mg-rich orthopyroxene; grouped with howardites
and eucrites in HED classification; [see Meteorites f
on HEDs]
- diopside
- CaMgSi2O6; one corner of pyroxene
quadrilateral [see also enstatite; ferrosilite;
hedenbergite]; midway between enstatite and
wollastonite
- dolerite
- see diabase
- dolomite
- CaMg(CO3)2; trigonal (-); perfect cleavage; twinning common;
extremely high birefringence; similar in appearance to calcite, several chemical
tests can be done to distinguish the two; associated with evaporite deposits,
altered ultrabasic rocks, hydrothermal veins, metamorphosed
limestones, etc.; [DHZ 489]
- drusy
-
having many druses: a. An irregular cavity or opening in a vein or rock, having its interior
surface or walls lined (encrusted) with small projecting crystals
usually
of the same minerals as those of the enclosing rock, and sometimes
filled
with water; e.g., a small solution cavity, a steam hole in lava, or a
lithophysa in volcanic glass.
b. A mineral surface covered with small projecting crystals; specif. the
crust or coating of crystals lining a druse in a rock, such as sparry
calcite filling pore spaces in a limestone. DMMRT
- dunite
-
intrusive, ~90% olivine; minor phases include chromite,
magnetite, ilmenite, & pyrrhotite
Go To Top
- endogenic
- (also endogenous, endogenetic) produced or growing from
within
- enstatite
- A mineral of
the pyroxene group of silicates containing magnesium and no iron - MgSiO3; the
magnesium endmember of the pyroxene system [see also wollastonite,
ferrosilite, diopside, hedenbergite];
orthorhombic; also, a class of (chondritic?) meteorite.
- erionite
- type of zeolite
- eucrite
- A type of
achondrite meteorite made primarily from basaltic plagioclase and (Ca-)pyroxene;
three types: noncumulate, cumulate, and polymict;
grouped with howardites and diogenites in HED meteorite
classification; [see Meteorites f for HEDs]
- euhedral
- perfect crystal
shapes, well-formed faces
- eutectic
- least possible
temperature of solidification
- euxinic
-
1. describing an environment having restricted
circulation and stagnant or anaerobic conditions.
2. of or
relating to the material deposited in such environments and the
process of
its deposition.
(Harcourt)
Go To Top
- fasciculate
- having bundles,
tufts, or clusters of like plant parts growing out from the same area [from
biology; applies to mineral texture???]
- fassaite
-
type of pyroxene with high Al, high Ca, high ferric/ferrous Fe [DHZ 120]
- ferrosilite
- FeSiO3; iron
endmember of pyroxene system [see also enstatite, wollastonite; diopside, hedenbergite]
Go To Top
- gabbro
-
intrusive version of basalt; "coarse-grained intrusive igneous rock...
characterized by a dark color and clinopyroxene" [Harcourt]
- glomerophyric
- texture in a porphyritic rock where phenocrysts are
clustered in irregular groups; also cumulophyric
- granite
- coarse-grained
plutonic rock, mostly quartz and feldspar with minor mica or other colored
minerals, such as hornblende, biotite, or muscovite; rich in Si and K
- granoblastic
- texture of
metamorphic rocks where recrystallization has formed equidimensional crystals;
often, interlocking grains of a mineral meet at 120°; [see http://www.geolab.unc.edu/Petunia/IgMetAtlas/meta-micro/granoblastic.X.html
for an example]
- granophyre
-
rock dominated by quartz and feldspar intergrowth (granophyric
texture); may represent the most differentiates portions of mafic
intrusions; found in small sills and dikes in highly differentiated, layered
intrusions; see [http://www.geolab.unc.edu/Petunia/IgMetAtlas/plutonic-micro%7F/granophyre.X.html
and http://sorrel.humboldt.edu/~jdl1/web.page.images/granophyre1.html
for examples]
- granophyric
- igneous texture, irregular intergrowth of quartz and feldspar; disconnected qu
grains extinguish simultaneously under XPL, enclosed in host feldspar
- granular
-
igneous texture where the crystals are all roughly the same size; often
[but not always?]
implies metamorphism.
Contrast seriate.
- granulitic
-
texture made of augite and/or olivine between
laths of plagioclase
[Penguin]. Also called intergranular.
"relating to a rock structure that results from the
production of granular or flattened fragments
in a rock by crushing...a granular igneous rock texture in
which all or nearly all the components are xenomorphic"
[Harcourt]
Granulitic impactites are a suite of lunar rocks which are not
really granulites at all!
- graupen
- ??? lenticular clay
clast; plural of graupel? (German word for "snow pellet")
Go To Top
- halloysite
- Al2Si2O5(OH)4, a white, monoclinic, clay mineral of the
kaolinite-serpentine
group; hydrated form; polymorphous
with dickite, kaolinite, and nacrite; specific gravity of 2.0 to 2.2;
hardness of 1 to 2.5 on the Mohs scale
- hedenbergite
- CaFeSi2O6; one corner of
the pyroxene quadrilateral [see also diopside, enstatite, ferrosilite]
- Hesperian
- Middle age of Martian
history; 3.5
- 1.8 Ga (Hartmann
& Tanaka) or 3.8 - 3.55 Ga (Neukum & Wide)
[EAA] [see also Amazonian, Noachian]
- hexahedrite
- type of iron meteorite made almost entirely of kamacite
and named for its cubic (hexahedral) cleavage of α-Fe,Ni single
crystals; Ni contents below 6%; no Widmanstätten pattern; designated H; most
belong to chemical group IIA; [compare octahedrite; ataxite]
- hydrothermal
-
\Hy`dro*ther"mal\, 1. Of or
pertaining to hot water; -- used esp. with reference to the action of
heated waters in dissolving,
redepositing, and otherwise producing mineral changes within the crust
of the globe.
2. Geology.
a.Of or relating to hot magmatic emanations rich in water.
b.Of or relating to the rocks, ore deposits, and
springs produced by such emanations. [www.dictionary.com]
- hypersthene
- orthorhombic
pyroxene; a pyroxene containing 22-30% FeSiO3.
- hyperthermophile
-
An organism which thrives at very high temperatures, ~80-100
o C; see also thermophile
- hypidiomorphic
-
of or relating to an igneous rock texture in
which the individual crystals are bounded partly by crystal faces and partly by
surfaces resulting from growth interference with other crystals
Go To Top
- iddingsite
- alteration
product of olivine; variable composition (broad term), red-brown to
orange-brown, hi birefringence (1.76-1.89), includes goethite & hematite; [DHZ, 4]
- ignimbrite
- pyroclastic
deposit; pumice, glass shards, and crystals deposited at high temperature
so that resulting rocks is consolidated; same as welded tuff,
although sometimes used for both welded and unwelded deposits; sometimes refers
to pumice-rich deposits [PR]
- illite
- group of clays;
most similar to micas; optical and physical properties vary, depending on hydration
& impurities; weathering or (hydrothermal) alteration product, favored by alkaline & hi-Al, hi-K conditions; extremely fine-grained
nature makes optical identification difficult [DHZ
260]
- ilmenite
- oxide, similar
to hematite; (Fe, Mg, Mn)TiO3 [DHZ, 412]
- immiscible
- incapable of
mixing or becoming homogeneous
- impact melt breccia
- melt-supported
breccia of impact melt and clasts, compare to suevite
- impactite
- any rock produced during
an impact (e.g. impact melt breccia, suevite,
tagamite)
- incompatible (element)
- an
element which "prefers" to be in the liquid state; last to crystallize out of a
melt; e.g., most of the REEs are incompatible
- indurate
- to harden or
become hard, as a soil lithifies into a rock
- intergranular
-
type of interstitial texture, with pyroxene, olivine,
or opaques filling the interstices between feldspar laths.
Also called granulitic texture.
- intersertal
- of or
relating to a texture of porphyritic igneous rock in which
glassy or partly glassy groundmass fills the interstices between unoriented
feldspar laths; [Harcourt] type of interstitial texture.
- interstitial
-
Texture with -something- between laths of feldspar; two varieties based on what
is occupying the
interstices: intersertal and intergranular. [Thank you,
random geo notes.]
- intrafasciculate
- see fasciculate. [???]
- isogyre
- dark cross
(uniaxial) or curve(s) (biaxial) of extinction visible in interference figure [see
detailed notes in Mineralogy
- General f]
- ITE
-
Incompatible Trace Elements
- -ite
-
suffix, when added to a mineral name, meaning a rock which consists
largely (>75%) of that mineral.
Go To Top
- jarosite
-
KFe(III)3(OH)6(SO4)2; common mineral in lower oxidized zone of ore deposits;
occasionally in volcanic igneous rocks as a late hydrothermal mineral;
hexagonal; optically (-); colorless-brown in section; occurs in crystal
aggregates, occasionally in euhedral crystals; distinct cleavage in {0001};
very high relief; extreme birefringence; alters readily to limonite [Kerr 262; not in DHZ]
Go To Top
- kamacite
- body-centered cubic
α-Fe,Ni; A metal composed of a nickel-iron alloy with up to 7.5 percent
nickel; a steel-gray, alpha-nickel-iron, body-centered cubic mineral, usually
containing 4-7.5% Ni; hardness of 4 on the Mohs scale; specific gravity of
7.85; found in meteorites
- kaolinite
- Al2Si2O5(OH)4; most common
type of
clay, also called kandite group;
forms from hydrothermal alteration of feldspars
& other silicates; acid conditions favor formation;
parent rocks usually silicic (granites, quartz diorites, etc.) [DHZ]; colorless or white; triclinic; polymorphous
with dickite, halloysite, and nacrite
- kink
- plastic deformation
feature; due to tectonics, squishing, or shock; low-pressure deformation,
present in shocked rocks but not diagnostic; also "kink band"
- KREEP
- Potassium (K) + Rare-Earth Elements (REE) + Phosphorus (P); forms at base of
crust; used as noun (e.g. certain pre-mare lunar basalts) or adjective (to describe any
rock rich in K, REE, and P).
- K-spar
-
potassium feldspar, KAlSi3O8;
one endmember of feldspar ternary system [see also albite,
anorthite]; different forms of K-spar include sanidines (hi-T,
monoclinic), orthoclase (lo-T, monoclinic), microclines
(lo-T, triclinic), and adularia.
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- labradorite
- type of
plagioclase
- lacrustine
- inland
depressions or damned riverine channels containing standing water; they can be
large or small areas and permanently or intermittently inundated; tranquil lake
environment as opposed to large ocean or flowing water in a river, etc.
- lamellar
- flat, plate like
individuals superimposed on and adhering to each other; describes mineral
aggregate; looks like parallel to subparallel stripes in thin section
- lamprophyre
- igneous rock, rich in alkalis, porphyritic, lots of mafic minerals
both in phenocrysts and groundmass; alnoite is one type, a minette is another
- laterites
- red residual
soil in humid or subtropical climate, leached of soluble minerals
- lechatelierite
- silica
glass, unstable below 1713 °C
- lenticular
- shaped like a
lens
- lherzolite
- a variety of peridotite containing abundant olivine with orthopyroxene and
clinopyroxene
- lignite
- brownish-black
coal at the intermediate stage of coalification between peat and bituminous
coal
- lime feldspar
- calcium
feldspar, CaAl2Si2O8; one endmember of feldspar ternary system [see also soda (albite), potash];
pure = anorthite
- lithophile
- "rock-loving" element,
"likes" to be in rocks [as opposed to siderophile];
officially: Said of an element with a greater free energy of oxidation per gram
of oxygen than iron. It occurs as an oxide and more often as an oxysalt, esp.
in silicate minerals. Examples are Se, Al, B, La, Ce, Na, K, Rb, Ca, Mn, U
- lodranite
- type of
primitive achondrite; related to acapulcoites
Go To Top
- marl
- A crumbly mixture of
clays, calcium and magnesium carbonates, and remnants of shells, used as
fertilizer for lime-deficient soils; designated as calcareous, clayey, or sandy
- mascon
-
mass concentration under mare basins on moon
- maskelynite
- plagioclase
which has been transformed by shock to glass; one type of diaplectic
glass
- mechanical
twins
- a crystalline twin formed by mechanical (plastic) deformation
- melatope
- dark areas
around the point of emergence of the optic axis (axes) in an interference
figure; dark areas at center of isogyre [see detailed notes
in Mineralogy - General f]
- melilite
- Ca, Mg, Fe, Na,
Al silicate, tetragonal; of the akermanits-gehlenite isomorphous series; found
in calcium-rich basic eruptive rocks and thermally metamorphosed siliceous
limestones & dolomites, abundant in alnoite
[DHZ 72]
- merrilite
- ???
- mesosiderite
- class of
stony-iron meteorite, about 50/50 by volume of each,
silicates are related to eucrites and diogenites, metal is Fe,Ni; weird mixture of "crustal" and
"core" material with no mantle-y stuff; [see Meteorites f]
- mesoperthite
- almost a perthite???
- mesostasis
- the most
recently formed glassy or aphanitic interstitial material of an igneous rock;
submicron intergrowth which may or may not contain glass; late-forming minerals
occur interstitially, forming complex mixture of fine-grained minerals and
glass [Heiken et al. 1991]
- metaclastic
- metamorphosed clastic rock ???
- metasomatism
- a
metamorphic process involving nearly simultaneous capillary solution and
deposition, by which one mineral or mineral assemblage replaces another of
different composition in the absence of melting; type of (hydrothermal)
alteration
- microdiastem
- small version of a diastem ???
- microcrystalline
- crystals are too small to
be seen with the naked eye, can only be seen with a microscope; contrast cryptocrystalline.
- micrographic texture
-
intergrowth pattern of two minerals; looks
like cuneiform writing; typical of a granophyre
- minette
- a syenitic lamprophyre consisting of biotite phenocrysts in
a groundmass of orthoclase and biotite [Harcourt]
- monomict
- description of a
breccia in which the matrix and clasts are of the same
class and type; as opposed to polymict; conatins no impact
melt
- montmorillonites
- group of clay minerals;
one type of smectite; color most often pink, buff, grey, or
lt. brown, many white; optical properties affected by hydration; alteration
product of eruptive basic igneous rocks, usually tuff &
ash, if drainage is poor & there is sufficient Mg (otherwise kaolinite), parents are usually Ca- or Na-rich, alkaline
conditions
- mylonite
- A chert-like rock
without cleavage but with a banded or streaky structure produced by extreme
shearing of rocks that have been pulverized and rolled during intense dynamic
metamorphism.
- mylonitization
- the
deformation of rock produced by intense microbrecciation,
resulting from the application of mechanical forces in a definite direction
without any appreciable chemical alteration of granulated materials; (also
mylonization)
- myrmekite
- special type of
symplectite; vermicular quartz
intergrowth with plagioclase; [see notes in Mineralogy: general f]
Go To Top
- nakhlite
-
one of a group of Martian (most likely) meteorites; clinopyroxenites;
include Nakhla, Lafayette, Governador Valadares. See also shergottites and chassignites.
- nepheline
- (Na, K)(Al,
Si)2O4; colorless to turbid in thin section; may have rows of inclusions; short
prismatic hexagonal crystals w/ hexagonal & rectangular sections; low
relief; low birefringence; alters readily to zeolites,
etc.; only in soda-rich igneous rocks (nepheline syenites, phonolites, some basalts) [Kerr
322]
- Noachian
- Earliest age of Martian
history; 3.5 - 4.6 Ga (Hartmann
& Tanaka) or 3.8 - 4.6 Ga (Neukum & Wide)
[EAA] [see also Amazonian, Hesperian]
- norite
- pyroxene (hypersthene) & plagioclase (labradorite)
gabbro; coarse-grained, igneous rock, generally basaltic in composition, but
with orthopyroxene as the major phase; type of lunar rock
- normal twins
- twin axis is normal to a possible crystal face, this face is
parallel to the composition plane [see also parallel
twins, complex twins]
- normal zoning
- trend of zoning expected for cooling magma; e.g. pyroxene gets more
Fe-rich towards edges, plagioclase gets more sodic
- nuée ardent
- literally, "glowing avalanche" or "glowing cloud;"
refers to pyroclastic flows which produce welded
tuffs, specifically used for those flows which are observed [PR]
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- octahedrite
- An iron meteorite
composed of taenite and kamacite, named
for the octahedral (eight sided) shape of the kamacite crystal
growth; show Widmanstätten pattern; further divided by
width of kamacite lamellae; [PM
4-6] [compare hexahedrite; ataxite]
- oikocrysts
- in a poikilitic
or poikiloblastic texture, the crystal that encloses
the other (the chadacryst); usually anhedral
- olivine bronzite
- name given
to H class ordinary chondrites as they are composed of
olivine and bronzite
- olivine hypersthene
- The name
given to L class ordinary chondrites as they are composed
of olivine and hypersthene
- ophiolite
-
Oceanic crust that has been thrust upward (instead of being subducted
downward, as is usual) and is now in the middle of continental crust.
- ophitic
- an igneous
rock texture that is characteristic of diabase or dolerite, which features lath-shaped plagioclase crystals
partly or completely embedded in pyroxene (commonly augite)
crystals; [a type of poikilitic texture;
also called poikilophitic]
- orogeny
-
The process of mountain formation, especially by a folding and faulting
of the earth's crust. adj., orogenic
- ortho-
- orthorhombic version
of a mineral??? [as opposed to clino- ]; literal meaning:
straight, not sloping; in metamorphic geology, a prefix used in front of
a metamorphic rock name indicating that
rock derived from an igneous rock (e.g. orthogneiss) [contrast para-].
- orthopyroxene
- Also orthorhombic pyroxene; any of
several members of the enstatite-ferrosilite
series (pyroxene group) that crystallize in the orthorhombic system, and
generally contain no calcium and little or no aluminum;
lower birefringence than clinopyroxene, and pleochroic in PPL.
- orthoclase
- One type of K-spar; KAlSi3O8; potassium
endmember of feldspar ternary system [see albite, anorthite]; also called potash
- Ostwald ripening
- Spontaneous process where lots of tiny crystals are incorporated into
larger crystals. Results in a
coarsening of rock texture (increase in mean grain size; decrease in
number of crystals). Occurs because large crystals have lower
surface-area-to-volume ratio, and are therefore energetically favorable,
although formation of smaller crystals is kinetically favorable.
See
Tutorial on Ostwald Ripening & references therein.
Go To Top
- palagonite
- general term
for hydrous, altered basaltic glass; yellow-brown, waxy, dull, resinous; [PR ch. 12]; see also detailed notes in Volcanics
Project f
- paleosols
- ancient soils,
preserved, kinda solidified [Celinda]
- pallasite
- class of
stony-iron meteorites; Fe-Ni metal forms a continuous framework enclosing
nodules of olivine; [see Meteorites f]
- para-
-
in metamorphic geology, a prefix added to a metamorphic rock name,
indicating the rock derived from a sedimentary rock, e.g., paraschist.
[contrast ortho-]
- paragenesis
-
characteristic assemblage of minerals in a
rock or an ore deposit, formed at the same time and apparently in
equilibrium. (Harcourt)
- paragenetic sequence
-
the chronological order of
crystallization of minerals or mineral assemblages in a rock or an ore
deposit
(Harcourt)
- parallel twins
- twin axis is a possible crystal edge, composition
plane is parallel to the twin axis and need not define a crystal face [see
also normal twins, complex twins]
- pedogenesis
- process of
soil formation
- pegmatite
- a light-colored
igneous rock or rock group from which feldspar, mica, or gemstones are derived;
characterized by very coarse grains of interlocking crystals, with typically
but not exclusively granitic composition
- peridotite
- dark, coarse-grained
plutonic rock or rock group, consisting primarily of olivine, with or without
mafic minerals such as amphiboles, pyroxenes, or micas; upper mantle material
- perthite
- intergrowth of
two minerals, specifically sodium [see soda, albite]
and potassium feldspars [see potash, orthoclase]
in which the sodium feldspar occurs as small strings, blebs, or films;
[opposite of antiperthite]; [see detailed notes in Mineralogy
- general f]
- petrography
- any
systematic classification of igneous and metamorphic rocks on the basis of
mineralogical and textural relationships, especially by means of microscopic
examination [Harcourt];
especially in hand sample and thin section [Penguin]
- petrology
- the scientific
study of rocks [Harcourt]
- phaneritic
-
a texture with grains that are big enough to see with the naked eye;
~ > 0.1 mm grains. Further subdivided into: Fine ( < 1 mm), medium (1-5
mm), coarse (5 mm - 3 cm), and very coarse ( > 3 cm).
[contrast aphanitic]
- phengite
- type of muscovite (mica) where Si:Al >
3:1; increase of Si is accompanied by substitution of Mg or Fe+2 for Al in
octahedral sites; [DHZ 202]; sericite
is also a type
- phenocryst
- in a porphyritic
texture, larger crystals which are embedded in fine-grained groundmass; not
necessarily all the same mineral
- phillipsite
- type of zeolite, common alt. prod. of more mafic (basaltic) glasses
- phonolite
- light-colored,
volcanic rock, lots of feldspars; includes nephelite, haynite, etc.; thin slabs
of it ring when struck, "clinkstone"
- picrite
- a dark, fine- to
medium-grained igneous rock with abundant olivine and smaller amounts of
pyroxene, hornblende, and plagioclase
- pigeonite
- type of
pyroxene, Ca-poor [DHZ, 129]
- pilotaxitic
-
texture with a felted mass of acicular or lath-like
crystals, which may
show flow structure [Penguin] (See also
trachytic)
- pleochroic
- said of a mineral which changes color
in PPL when polarizer is rotated 90 degrees; diagnostic of biotite, hypersthene,
hornblende, chlorite...
- plessite
- A mineral
composed of a fine-grained mixture of kamacite and taenite that fills in the wedges between kamacite
and taenite bands in iron meteorites.
- poikilitic
- igneous
texture; large crystal(s) of one mineral (oikocryst)
enclose lots of unoriented smaller crystals (chadacrysts)
of another mineral; [e.g., ophitic]
- poikiloblastic
- texture
similar to poikilitic, but formed by metamorphism and recrystallization rather
than solidification from a melt
- polymict
- description of a
breccia in which the clasts &/or matrix have differing
compositions; as opposed to monomict; no impact melt
- polymorph
-
same chemical composition, different structure under different P,T
conditions; e.g., calcite and aragonite.
- polysynthetic twinning
- repeated twinning
of crystal lamell[ae], as that of the triclinic feldspars;
composed of many lathlike individuals
- porphyritic
- an igneous
rock texture in which large phenocrysts are embedded within
a fine crystalline and/or glassy groundmass
- porphyry
- porphyritic
rock; first applied to a purple-red rock quarried in Egypt and
characterized by phenocrysts of alkali feldspar; usage: rock name descriptive
of the groundmass composition usually precedes the term; e.g., diorite porphyry
[DMMRT]
- potash
- See K-spar
- pseudotachylite
- black vein
rock superficially similar to tachylite but produced by extreme
mylonitization and/or partial melting; often used
descriptively, but specific meaning refers to formation of melt rocks by friction;
seen at impact sites such as Vredefort and Sudbury
- pyroclastic
- describes
clastic material ejected from volcanic vents [PR]; also
called ash, tephra, etc.; pyroclastic deposits include ignimbrites,
nuées ardentes, and welded tuffs.
- pyrrhotite
-
brownish-bronze iron sulfide mineral; FeS; weak magnetic properties, also
"magnetic pyrite"; FeS is approximate composition, usually contains less iron; troilite is type of pyrrhotite which is stoichiometric FeS; [DHZ 412]
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-
-
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- REE (Rare Earth Element)
-
chemically related, metallic elements with atomic numbers 57 - 71; special
row of the periodic table; specifically, lanthanum (La), cerium (Ce),
praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium
(Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium
(Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); most of these are incompatible elements.
- regmaglypt
- Depressions resembling (and
called) thumbprints that are produced on the surface of some meteorites during
atmospheric Itransit by material ablating (melting) off the
surface.
- relict
- mineral, structure, or
feature of a rock that persists despite processes that tend to destroy it, or
remains after parts have been destroyed
- rhabdite
- (Fe,Ni)3P; see schreibersite; specifically refers
to the morphology of small euhedral crystals in the shape of rods or platelets;
once thought to be a separate mineral
- rutile
- common form of
TiO2, reddish-brown; yellow-red-brown in PPL; hi relief, hi birefringence;
occurs as minute grains in igneous rocks & needles in quartz or mica [DHZ, 415]; [see notes in Mineralogy -general f]
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- saponite
- clay mineral,
hydrous silicate of Al & Mg; occurs in soft soapy amorphous masses in
cavities; fills veins in serpentine & cavities in taprock
- schlieren
- Irregular dark
or light streaks in plutonic igneous rock that differ in composition from the
principal mass; Regions of a transparent medium, as of a flowing gas, that are
visible because their densities are different from that of the bulk of the
medium [Webster's]; streaks of fine-grained debris, more common in impact melt
glass than in volcanic glass [PM 5-80]
- schreibersite
- (Fe,Ni)3P; a strongly magnetic,
silver to tin-white, metallic,
tetragonal mineral that tarnishes to brass-yellow or
brown; occurs as very small euhedral tablets, plates, needles,
or rods; or as coarse irregular or skeletal inclusions; specific gravity
of 7.0 to 7.8; hardness of 6.5 to 7
on the Mohs scale; found in all iron
meteorites. (also rhabdite)
- scoria
- highly vesicular
basalt
- seriate
- texture in which
crystals show a continuous range of sizes
- sericite
-
fine-grained type of white mica (muscovite or paragonite); can be chemically
same as muscovite, but often high SiO2, MgO, H20, & low K2O; occurs in
silky scales with a fibrous structure; characteristic of sericite schist;
replaces feldspars; can be product of hydrothermal alteration; phengite is also
a type; [DHZ 202]
- shergottite
- class of rare
achondritic meteorites, geologically youngest of any meteorites;
'S' of SNC;
[see Volcanics Project f; DaG476 f; QUE94201 f]; believed
to be of Martian origin; basaltic and lherzolitic;
include Shergotty, Zagami, EETA79001, Que94201
- sideromelane
- basaltic glass, transparent. See tachylite.
- siderophile
-
"metal-loving" elements, "like" to be in metallic form [as opposed to lithophile]; officially: Said of an element concentrated in
the metallic rather than in the silicate and sulfide phases of meteorites, and
probably concentrated in the Earth's core relative to the mantle and crust; or,
Said of an element with a weak affinity for oxygen and sulfur, and readily
soluble in molten iron; Examples are Fe, Ni, Co, P, Pt, Au
- sinter
- precipitate from hot or
cold mineral waters; may contain silica (siliceous sinter) or calcium carbonate
(travertine); specifically [?] precipitates of hydrothermal systems
- size
-
Despite the stated opinions of some maleologists, size is important. For size terms
for hand samples, see aphanitic (small) and
phaneritic (big). For a discussion of "granulometric
classifications," see
Qualifiers,
etc. recommended by the SCMR (this applies to metamorphic rocks,
but it still might be handy). For igneous petrology, the terms
fine-grained (< 1 mm), medium-grained (1-5 mm), and coarse-grained
(>5 mm) are used.
- smectite
- hydrous silicate
of Al; greenish, ~transparent, ~gelatinous-looking; "swelling"
clay (takes in water between layers); occur most commonly in fine-grained
aggregates, often vermiform, lamellar,
or spherulitic; birefringence higher than most kaolinites & lower than most
illites; usually not identifiable optically, need other method e.g. X-ray
powder, dehydration curves, etc.; weathering product of mafic rocks,
hydrothermal alteration product near metalliferous veins or deposits; alkaline conditions favor formation [see montmorillonite,
kaolinite] [DHZ
264]; formation favored in
marine environments
- soda
- sodium feldspar, NaAlSi3O8; pure form
= albite; one endmember of feldspar ternary system; [see also
orthoclase, anorthite]
- sodic
- - sodium-rich, as in plagioclase
- sorption
- process by which
one substance takes up another (by ADsorption or ABsorption)
- spherulite
- radiating mass
of fibrous crystals in a glassy matrix
- spicules
- A small
needlelike structure or part, such as one of the silicate or calcium carbonate
processes supporting the soft tissue of certain invertebrates, especially
sponges.
- stony-irons
- see mesosiderite; pallasite
- subhedral
- describes a
crystal with imperfectly developed faces
- subophitic
-
a somewhat less-than-ophitic (poikilitic)
texture, where plagioclase encloses pyroxene only partially.
Penguin
- subsidence
- a
settling/sinking down/displacement of sediments, specifically, in a vertically
downward direction
- subsolidus
- as a melt solidifies,
crystals continue to change while rock is solid but still hot; reactions occur
at temperatures below melting point (below solidus)
- suevite
- impact breccia with fragments of impact melt (clasts); grain-supported,
compare to impact melt breccia
- sutured
- texture in which
mineral grains or irregularly shaped crystals interfere with one another,
resulting in interlocking, suture-like contacts without interstitial spaces
- symplectite
- intergrowth of
two (three) minerals; usually in high-grade metamorphosed rocks, related to
decompression; myrmekite is one type; [see notes in
Mineralogy - general f]
- syenitic
- a crystalline
plutonic rock, or rock group, characterized by granular texture and consisting
principally of alkali feldspar, with small amounts of
plagioclase and mafic minerals, and possibly traces of quartz; it is the
intrusive equivalent of trachyte [Harcourt]
- syn-
- prefix meaning
"together" (e.g. "syndepositional")
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- tabular
- looks ~ lamellar in thin section (thin stripes); describes crystals
which are tab-shaped; flat or flat-surfaced
- tachylite
- (also tachylyte)
Variety of basaltic glass, partly or completely charged with microlites of
Fe/Ti oxides, which are microcrystalline & therefore
opaque in transmitted light (vs. sideromelane,
which is transparent; which forms is dependent on cooling rate) [PR, 76]; black to brown or green volcanic glass of
basaltic composition
- taenite
- face-centered cubic γ-Fe,Ni
with varying Ni content (~ 27% to 65%) (may be more complex);
silver-white to grayish, metallic,
magnetic; found only in meteorites; specific gravity of 7.8 to 8.22; hardness
of 5 to 5.5 on the Mohs scale; 27-74% nickel and a little cobalt
- tagamite
- impact melt rock, more
specifically breccias which underlie and overlie melt sheet [Grieve et al.
1977]
- tektite
-
A form of natural glass that, in many specimens, exhibit aerodynamic
shaping caused by atmospheric passage while molten. Origin is not known, but a
possibility is that they represent drops of molten silicates
"splashed" out from meteorite impact events.
- tetrataenite
- FeNi metal, with 50±2 wt % Ni, cubic structure; see also taenite, kamacite
- thermophile
-
an organism which thrives at high temperatures, >50o C;
see also hyperthermophile
- tholeiite
- a silica-oversaturated basaltic rock, or rock group, containing
phenocrysts of plagioclase, pyroxene, and iron oxide minerals in a glassy
groundmass
- tonstein
- an argillaceous rock predominantly composed of the
clay mineral kaolinite and some detrital and carbonaceous
material; it occurs as thin bands in coal seams
- trachyte
- compositionally
between rhyolite & phonolite, high Si (not as high as
rhyolite), high Na & K (not as high as phonolite); extrusive
- trachytic
-
volcanic texture where alkali feldspar crystals are
aligned by flow [Penguin]
- tridymite
- SiO2, a
colorless or white monoclinic pseudohexagonal or triclinic mineral occurring in
minute, commonly twinned, tabular crystals and crystal aggregates in acidic volcanic rocks and stony meteorites; specific gravity of
2.26; hardness of 7 on the Mohs scale; polymorphous with coesite, cristobalite,
quartz, and stishovite
- troctolite
- coarse-grained
igneous rock, generally basaltic composition, mostly plagioclase and olivine,
little to no pyroxene
- troilite
-
brass colored sulfide of
iron (FeS); common to many types of meteorites & occurs mainly in
meteorites; type of pyrrhotite; non-magnetic; [DHZ 412]
- twinning
- The assemblage of two or more crystals,
or parts of crystals, in reversed position with reference to each other in
accordance with some definite law; also, rarely, in artificial twinning
(accomplished for example by pressure), the process by which this reversal is
brought about. Note: The relative
position of the parts of a twin may be explained by supposing one part to be
revolved 180 degrees
about a certain axis (called the twinning axis),
this axis being normal to a plane (called the twinning
plane) which is usually one of the fundamental planes of the crystal.
This revolution brings the two parts into parallel position, or vice versa. A
contact twin is one in which the parts are united by a plane surface, called
the composition face, which is usually the same as the
twinning plane. A
penetration twin is one in which the parts
interpenetrate each other, often very irregularly. Twins are also called,
according to form, cruciform, geniculated, etc.
[Webster's] Present in many crystals, most typically feldspar,
also calcite, dolomite, pyroxene, amphibole, etc. [see polysynthetic
twinning, normal twinning, parallel
twinning, complex twinning, Albite
twinning, Carlsbad twinning]
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- unconformable
- relating to rock strata that do not
represent part of a continuous whole with underlying (older) rocks, with
respect to position, age, etc.; contrast conformable
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- variolitic
- of basic igneous rock,
having a fine-grained texture characterized by varioles [Harcourt]
- varioles
- a small, pea-sized
spherical body in igneous rock, usually composed of fanlike sprays of
plagioclase or pyroxene crystals radiating outward from a central point [Harcourt]
- vermicular
- (also vermiform) worm-shaped
- vuggy
- having
vugs, or small cavities
in a vein or rock, usually lined with crystals of different mineralogical
composition from the enclosing rock
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- welded tuff
- pyroclastic
deposit, deposited at high temperature so that ash is relatively
consolidated; same as ignimbrite, Nuée Ardente
- whitlockite
- Ca9(Mg,Fe+2)H(PO4)7; type of phosphate; a colorless, white, gray or pinkish,
transparent to translucent, trigonal mineral, having a specific gravity of 3.13
and a hardness of 5 on the Mohs scale; occurs as a secondary mineral in granite
pegmatites and in phosphate rock deposits, and has been identified in lunar
rocks
- Widmanstätten pattern
- texture visible in many iron meteorites (called octahedrites)
and pallasites; oriented intergrowth of kamacite
and high-Ni (taenite, or more complex, variation in Ni
across lamellae) lamellae; visible when polished surface is etched with nital
(nitric acid in solution with ethanol)
- winonaite
- ???
- wollastonite
- CaSiO3;
represents calcic endmember of pyroxene system [see also enstatite,
ferrosilite; diopside, hedenbergite],
not usually shown in diagram, but used in Wo#En#Fs#; not technically a pyroxene (different structure)
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- xenocryst
- A crystal in an
igneous rock that is foreign to the body of rock in which it occurs; [see chadacryst]
- xenomorphic
-
igneous texture where crystals are not bounded by crystal
faces; instead, shape is determined by "
adjacent preexisting crystals" [Harcourt]
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- yardang
-
sharp, irregularly-crested ridges carved by the wind and oriented
parallel to the wind. [IGGT]
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- zeolite
- One of a group of hydrated
aluminosillicates of alkali and alkaline earth
metals; 2nd most common alteration product of volcanic rocks
(after smectites); general formula:
XuYrZnO2n x mH2O,
where X=(Na,K), Y=(Ca,Sr,Ba,Mg), and Z=(Al,Si).
See detailed notes in W. Clearwater f
- zoning
- an imperfect reaction in
crystal growth between the solid and liquid phases, resulting
in variations in the chemical
composition within the crystal; [see normal zoning]
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Reference Codes:
DHZ = Deer, Howie and Zussman (1978) An Introduction to
the Rock Forming Minerals.
DMMRT = Dictionary of Mining, Mineral, and Related Terms;
http://imcg.wr.usgs.gov/dmmrt/
EAA = Encyclopedia of Astronomy and Astrophysics,
http://www.ency-astro.com/
Harcourt = Harcourt Academic Press Dictionary of Science and Technology; http://www.harcourt.com/dictionary/
IGGT = Illustrated Glossary of Geologic Terms, by Steven M. Richardson,
Iowa State University.
http://www.geology.iastate.edu/new_100/glossary.v2.html
Kerr = Kerr(), Optical Mineralogy
Penguin = The New Penguin Dictionary of Geology, by P. Kearey.
PM = Papike (1998) Planetary Materials, Reviews in Mineralogy 36
PR = Fisher and Schmincke (1984) Pyroclastic Rocks.
