Millington Jr. High – Rocks and Minerals January Practice Test 2014
Intrusive ( I ) or
Extrusive (E)
Classify the following igneous rocks:
Andesite
Usually blackish-brown, sometimes greenish. Papier-mache
look.Contains less than 5% quartz.
Basalt
Very dark, often black. Often contains phenocrysts of feldspars,
olivine, and other dark minerals
Diorite
Dark gray to blackish gray, mottled. Evenly speckled with dark
and light minerals, salt-and-peppery look.
Gabbro
Gray or light green, very coarse-grained.
Granite
Crystals of feldspar (pink or red), mica (dark brown or black),
and quartz (clear pink, white, or black).Coarse-grained
Obsidian
Shiny black.Volcanic glass, has a conchoidal fracture (see
explanation of cleavage and fracture below) Be careful
Pegmatite
Same composition as granite but has very large, usually light
crystals.
Pumice
Very light gray. Also volcanic glass, but very light and bubbly.
Only rock that floats.
Rhyolite
Usually light grayish-pink. Made of the same minerals as
obsidian and pumice, but did not cool as quickly.
Scoria
Dark gray, red, or black. Composed of basalt that cooled very
quickly with trapped air, so it is bubbly-looking.
Fill in the blanks of this chart
Metamorphic Rocks
Name
Parent
Description
Gneiss
Marble
Metamorphism
Medium to
coarse
grained.
White or gray, but foliated
with dark rock. Must be
less than 50% foliated.
High grade
metamorphism
The metamorphism of
limestone or dolomite.
Very fine
grains, wavy
bands.
Light, silvery-gray to leadgray. Silky sheen
Silvery-gray, banded,
wavy. Must be more than
50% foliated with dark
rock.
Almost any
rock.
Fairly small
particles.
Quartzite
Slate
Color and Foliation
Calcite or
limestone
Phyllite
Schist
Grain
Shale
The metamorphism of
sandstone.
Dark gray, shiny
Metamorphism
Place the minerals and objects in order of Mohs Hardness
1
2
2.5
3
3
4
5
5.5
6
6
7
7
8
9
10
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
Apatite
Calcite
Copper penny
Corundum
Diamond
Feldspar
Fingernail
Fluorite
Gypsum
Knife blade
Quartz
Steel file
Talc
Topaz
Window glass
Mineral Name Description
Using the following definitions, use the definitions to describe the following
specimans: The most correct definitions for each specimen.
Obsidian
Gold
Graphite
Galena
Sandstone
Shale
Gabbro
Pumice
Quartz
Dolomite
Hematite
Definitions
Copied shamelessly from the National Audubon Society Field Guide to North American Rocks
and Minerals
accessory mineral
a mineral that occurs in a rock in minute quantities, and does not affect the way the rock
is named for classified
acidic rock
a type of igneous rock (i.e. granite) that consists predominatly of light-colored minerals
and more than 66% free or combined silica (see basic rock, intermediate rock, and
ultrabasic rock)
alkaline rock
a rock containing more than average amounts of potassium- and sodium-bearing
minerals
alteration
any physical or chemical change in a mineral or rock subsequent to original formation;
usually results in the formation of new minerals or in textural changes in the rock
amorphous
literally, "without form"; applied to rocks and minerals that lack definite crystal structure
amphiboles
a group of closely related, dark-colored rock-forming silicate minerals (e.g. actinolite,
hornblende, glaucophane, and tremolite)
amygdaloidal rock
a volcanic rock containing numerous gas cavities (amygdules) filled with such secondary
minerals as calcite, quartz, and zeolites.
amygdule
a mineral-filled cavity formed in an igneous rock by escaping gas
anthracite coal
a hard, black, lustrous coal
aphanitic rock
a rock in which the crystalline constituents are too small to be distinguished with the
unaided eye
argillaceous
containing or composed largely of clay (e.g. argillaceous shale, etc.)
arsenates
minerals (e.g. adamite) in which the arsenate radical (AsO4) is an important constituent
basic rock
an igneous rock (e.g. gabbro) with low silica content and a high percentage of pyroxene,
hornblende, and labradorite (see acidic rock, intermediate rock, and ultrabasic rock)
batholith
a huge body of plutonic rock that has been intruded deep into the earth's crust and later
exposed by erosion
bedding
the arrangement of sedimentary rocks in approximately parallel layers (strata, or "beds"),
which correspond to the orignial sediments that formed the rock
bituminous rocks
rocks that contain (and sometimes smell of) asphalt, tar, or petroleum
borates
a group of minerals (e.g. borox, colemanite) in which the borate radical (BO3) is an
important constituent
botryoidal
resembling a bunch of grapes; describes hematite and a number of other minerals in
which very small radiating crystals are arranged in massive clumps, giving a surface
covered with spherical bulges (from Greek botrys, "bunch of grapes")
calcareous
containing calcium carbonate or calcite
calcic
containing calcium
carbonaceous
composed largely of organic carbon (i.e. carbon derived from plant and animal tissue)
carbonates
minerals (e.g. calcite) in which the carbonate radical (CO3) is an important constituent
cataclastic rock
a metamorphic rock produced by the crushing and grinding of preexisting rocks, which
are still visible as crushed and flattened minerals and as angular fragments (from the
Greek klastos, "broken")
cataclastic metamorphism
a metamorphism due principally to directed pressure and resulting in rocks with
cataclastic texture
characterizing accessory mineral
a mineral that gives a specific name to an igneous rock. In hornblende granite, for
example, hornblende is the characterizing accessory mineral
chemical sedimentary rock
a rock formed by chemical processes; gypsum is a chemical sedimentary rock, formed
by chemical precipitation
clastic rock
a sedimentary rock that is made up of fragments of preexisting rocks, transported
mechanically into the place of deposition
clay
any soft sediment or deposit that is very plastic when wet and consists of very finegrained, micalike materials, mainly hydrous aluminum silicates
cleavage
the tendency of some minerals to break along one or more regular, smooth surfaces
concordant
describes an intrusive igneous body whose surfaces are parallel to the bedding (or
foliation) of the surrounding rocks
concretion
an accumulation of mineral matter, formed when particles of silica, pyrite, gypsum, etc.
become cemented together into an orderly, rounded, often artificial-looking form
cross-bedding
an arrangement of layers within a sedimentary rock, such that minor layers lie at an
angle to the main layers of sediment; usually a sign of changing wind or water currents
action on the orignial sediments forming the rock
crystal
a solid mass of mineral, having a regular geometric shape and bounded by smoth, flat
surfaces (crystal faces)
crystal habit
the actual form of a crystal; determined by the shape and relative proportions of the
crystal faces
crystal symmetry
the repeat pattern of crystal faces, caused by the ordered internal arrangement of a
mineral's atoms
detrital sediment
a deposit of mineral and rock fragments that have been transported to their place of
deposition
differentiation
a process by which different types of igneous rocks are derived from the same parent
magma
dike
a wall-like body of igneous rock, usually intrusive, that cuts across the layers of
surrounding rocks
discordant
describes an intrusive igneous body whose margins cut across the bedding (or foliation)
of the surrounding rocks
dynamothermal metamorphism
metamorphism resulting from the combined effects of heat and pressure; also called
regional metamorphism
epithermal vein
a vein formed at shalow depths from ascending hot solutions
equigranular rock
a rock whose mineral particles are of the same general size
essential minerals
the mineral constituents of a rock (usually an igneous rock) that are used to classify and
name the rock
extrusive rock
an igneous rock that solidifies on the surface of the earth
feldspar
a group of abundant rock-forming silicate minerals, including orthosclase and microcline
(potash feldspars) and albite, oligoclase, andesine, labradorite, bytownite, and anorthite
(the plagioclase, or soda-lime, feldspars)
feldspathic rock
a rock that contains feldspar as a principal constituent
feldspathoids
a group of minerals (e.g. leucite, nepheline, and sodalite) that are similar in composition
to the feldspars, but contain less silica
ferruginous
containing iron
flow banding
a structure (in some volcanic rocks) consisting of alternating layers of unlike
mineralogical composition and formed as a result of flowing lava
foliation
the laminated structure present in regionally metamorphosed rocks that results from
segregation of different minerals into roughly parallel layers
fragmental rock
sedimentary rock consisting of rock and meineral fragments
friable
easily crumbled or pulverized
fusion
the process of being melted or dissolved by heat
gneissose rock
A rock that has the banded appearance of a gneiss but is not formed by metamorphism
granulose
a metamorphic texture characterized by granular minerals, such as quartz, feldspars,
and garnet, in alterating streaks and bands
groundmass
see matrix
halides
a group of minerals (e.g. halite and flourite) that are primarily compounds of the halogen
elements: bromine, chlorine, flourine, and iodine
hardness
resistance of a mineral to abrasion or scratching
hydrothermal alteration
an alteration of minerals or rocks by the action of superheated mineral-rich fluids, usually
water that has been heated to very high temperatures within a crystallizing magma
hydrothermal metamorphism
changes in the structure or composition of rock, caused by the action of hyrdrothermal
fluids
hydrothermal replacement
a change in a rock or mineral deposit due to the addition or removal of minerals by
hydrothermal fluids
hypothermal vein
a vein formed at relatively great depth and at relatively high temperatures (300-500 C)
igneous
rock formed by the solidification of magma
intermediate rock
igneous rock (e.g. syenite or diorite) that is transitional between acidic and basic rock,
having a silica content of between 54% and 65% (see acidic rock, basic rock, and
ultrabasic rock)
intrusive
an igneous rock that formed underground, from magma that was squeezed into cracks
or crevices, or between layers of older rocks
"Japanese" twins
simple contact twins (in quartz) in which two single crystals, usually boroad flattened
prisms, are joined in the same plane at an anble of about 84 degrees
laccolith
a lens-shaped body of igneous rock with a dome-shaped upper surface and a flat bottom
surface, and with both surfaces parallel to the bedding or foliation of the enclosing rocks
lamellar
composed of thin layers, plates, or scales
laminated rocks
sedimentary rocks that are formed of numerous very thin layers
lava
molten rock material extruded onto the surface of the earth
lava flow
a body of rock fromed by a single outpouring of lava
lenticular
lens-shaped
lopolith
a large, lenticular, centrally sunken mass of igneous rock whose surfaces are
concordant with the enclosing rocks
luster
the surface appearance of a substace, or the manner in which it reflects light
magma
molten rock material, beneath the solid crust of the earth, that solidifies to form igneous
rocks at or below the earth's surface
magmatism
any process by which magma solidifies into volcanic or plutonic rock
massive mineral
a mineral that occurs either without any definite external crystal form or in poorly defined
masses of small crystals
matrix
the fine-grained material (groundmass) that surrounds the larger crystals or particles in a
porphyritic or sedimentary rock. Also, any material, such as clay or rock, in which a
crystal, fossil, etc. is embedded
mesothermal vein
a vein that forms at intermediate depth and temperature
metamorphic
any rock (e.g. schist, gneiss, etc.) that was formed in some fashion from a preexisting
rock, trough heat, pressure, the effect of superheated fluids, or any combinatino of these
forces
mica
a group of solf silicate minerals (e.g. biotite, muscovite) that have perfect basal cleavage
in one direction and can easily be split into characteristic thin, elastic, pearly sheets
microcrystalline rock
a rock whose crystals are too small to be seem without a microscope (see aphanitic
rock)
mineral environment
the rock (or rock type) in which a mineral or a group of associated minerals forms and
occurs. Mineral environments include igneous, sedimentary, and metamorphic rocks as
well as several types of veins and replacement depostis
mineral stability
the ablility of a mineral to remain unaltered over a stated range of pressure and
temperature
molybdates
a group of minerals (e.g. wulfenite) in which the molybdate radical (MoO4) is an
important constituent
nodular
having the shape of or composed of irregular lumps of rock or mineral (e.g. nudular
chert)
organic compounds
compounds produced in or by plants and animals and containing carbon as the essential
ingredient
outcrop
a mass of bedrock that is exposed at the surface of the earth
oxides
a group of minerals (e.g. cuprite and magnetite) in which oxygen, combined with a metal,
is a major constituent
oxidized zone
the part of an ore body (usually the upper part) that has been altered by downward
percolating groundwater, containing dissolved oxygen and carbon dioxide
parting
the tendency of some minerals to separate along certain planes, which are not related to
the crystal symmetry of the mineral; usually due to twinning or deformation
pegmatite
an igneous rock of extremely coarse grain size. Usually found as dikes within a larger
plutonic or metamorphic rock mass, pegmatites are often excellent sources of large, fine
crystals, especially of quartz, tourmaline, feldspar, and mica
petrography
the branch of geology that deals with the description and classification of rocks
petrology
the study of rocks, specifically their composition, origin, and modes of occurence
phaneritic rock
an igneous rock in which all of the essential minerals can be distinguished with the
unaided eye
phenocryst
a prominent crystal (in a porphyritic rock) surrounded by smaller mineral grains
phosphates
a group of minerals (e.g. apatite) in which the phosphate radical (PO4) is an improtant
constituent
pipe
a vertical, cylindrical mass of igneous rock
pisolitic
consisting of rounded grains like peas or beans
placer
a deposit of heavy mineral particles (e.g. gold) that have weathered out of the bedrock
and been concentrated mechanically, usually by the action of streams
playa
a desert plain; a shallow basin in which water collects following a rain and is evaporated
plug
the solidified core of an extinct volcano
pluton
any deep, intrusive igneous body, of any size, whose exact form has not been
determined
plutonic rock
a granular igneous rock that has solidified at great depth and shows distinct grain texture
(e.g. granite, granodiorite)
porphyritic rock
an igneous rock in which larger crystals (phenocrysts) are enclosed in a fine-grained
groundmass, which may be crystalline or glassy
precipitation
the process by which a suspended or dissolved solid is separated out of a liquid
psuedomorph
a mineral that has taken the outward crystal form of a different mineral
pyroclastic
an extrusive rock made up of material ejected explosively from a volcanic vent
pyroelectricity
an electric charge produed in a crystal by heat
pyroxenes
a group of closely related, dark-colored rock-forming minerals (e.g. augite, diopside, and
acmite)
radical
a group of oxygen atoms clustered about a nonmetallic atom (e.g. silicon, phosphorus,
sulfur) so as to form a "structural unit" that behaves like a single atom
replacement
a process by which one mineral replaces another, while often retaining the physical form
of the first mineral
secondary minerals
minerals that are formed by the alteration of preexisting (primary) minerals
sedimentary
a layered rock, formed through the accumulation and solidification of sediments, which
may originally be made up of minerals, rock debris, or animal or vegetable matter
silica
silicon dioxide (SiO2), a tremendoulsy abundant mineral that occurs widely an in many
forms, including quartz, chalcedony, opal, and chert
silicates
a group of minerals (e.g. quartz, and orthoclase) composed essentially of SiO4
tetrahedra in different arrangements
sill
a tabular, sheetlike body of intrusive igneous rock, which has been injected between
layers of sedimentary or metamorphic rock
slaty cleavage
a variety of foliation typical of slates and characterized by parallel arrangement of clay
minerals
stock
a small, irregularly shaped body of intrusive igneous rock with a surface area of less
than 65 square kilometers
streak
the color of the powder of a mineral produced by rubbing the mineral over the surface of
a piece of unglazed, white porcelain
striations
minute parallel grooves or narrow channels on crystal faces
structure
large features of rock masses, such as flow banding and bedding; in minerals, structure
refers to the shapes and forms of crystal groups and masses
sulfates
a group of minerals (e.g. gypsum and barite) in which the sulfate radical (SO4) is an
important constituent
sulfides
a group of minerals (e.g. pyrite, galena, and sphalerite) in which sulfur is in combination
with one or more metals (copper, iron, or zinc)
sulfosalts
a group of minerals in which sulfer combines with the semi-metals (arsenic, anitmony,
and bismuth) to form what are called negative ions/anions, which then combine with the
metals (lead, silver, copper, and zinc) to form such minerals as enargite, tetrahedrite,
and pyrargyrite
tenacity
the ability of a substance to resist separation
texture
the surface appearance of a homogeneous rock or mineral aggregate. The degree of
crystallization, the size of the crystals, and the shape and interrelations of the crystals or
other components all contribute to the texture of a rock
tungstates
a group of minerals (e.g. scheelite) in which the tungstate radical (WO4) is an important
constituent
twin
a specimen that consists of two or more single crystals of the same mineral, intergrown
in a definite systematic arrangement
ultrabasic rock
any plutonic igneous rock (e.g. peridotite) with very low silica content (less than that of a
basic rock) (see acidic rock, basic rock, and intermediate rock)
vanadates
a group of minerals (e.g. vanadinite) in which the vanadate radical (VO4) is an important
constituent
vein
a tabular or sheetlike body of mineral matter (e.g. quartz) cutting across preexisting rock
(e.g. granite or gneiss)
vesicle
a small cavity in a volcanic rock
vitreous
glasslike in appearance and texture
volcanism
the movement of molten rock, by way of volcanoes, fissures, vents, etc., to the earth's
surface, where it cools into extrusive (volcanic) igneous rocks
volcano
a vent or hole in the earth's crust through which magma (in the form of lava), gases,
ashes, and other products escape to the surface
zeolites
a group of hydrated aluminosilicates of potassium, sodium, and calcium that can lose
part or all of their water (reversibly) without changing crystal structure. This open
structure allows the zeolites to absorb other compounds, making them commercially
valuable as purifiers and water softeners