Minerals Flashcards
anhydrite
a granular, white, anhydrous (water-lacking) calcium sulfate (CaSO4).
Andesite
A volcanic rock that in chemical composition is intermediate between basalt and granite.
Aragonite
A calcium carbonate mineral (CaCO3) that differs from calcite in its crystal form. (Aragonite is orthorhombic rather than rhombohedral as in calcite.)
Augite
A complex aluminous silicate of calcium, iron and magnesium, crystallising in the monoclinic system, and occurring in many igneous rocks, particularly those of basic composition. It is an essential component of basalt, dolerite and gabbro.
Basalt
Highly mafic igneous volcanic rock, typically fine-grained and dark in color; rough volcanic equivalent of gabbro.
Bowen’s Reaction Series
the sequence in which minerals crystallize from a cooling basaltic magma.
Calcite
The crystalline form of calcium carbonate, showing trigonal symmetry and a great variety of mineral habits. It is one of the commonest of minerals in association with both igneous and sedimentary rocks.
Carbonate clasts
sand or gravel sized pieces of carbonate. The most common clasts are either bioclasts (skeletal fragment of marine invertebrates) or ooids (Fig 4-39 C), which are spherical grains formed by the precipitation of carbonate around a nucleus.
Carbonate spar
clear, crystalline (sparry) carbonate. It occurs between clasts as a cement.
Chert
A dense, hard sedimentary rock or mineral composed of sub microcrystalline quartz. Unless colored by impurities, chert is white, as opposed to flint, which is dark or black.
Chlorite
A group of allied minerals which may be regarded as hydrated silicates of aluminium, iron and magnesium. They crystallise in the monoclinic system and are green in colour. They occur as alteration products of such minerals as biotite and hornblende, and also in schistose rocks.
Clastic sediment
sediment consisting of broken or eroded pieces of pre-existing rocks or minerals.
Clay mineral
silicates of hydrogen,aluminum,magnesium,iron, and potassium. Their basic structure is similar to that of mica but individual flakes are extremely small (some are as small as viruses). This means their mica-like form can be seen only with an electron microscope (Fig 4-15). Clay minerals form as a result of weathering of other aluminosilicate minerals, such as feldspars.
Cleavage
the tendency of a mineral to break evenly along one or more bright, planar surfaces.
Color
A mineral’s most conspicuous characteristic.
Coal
black, soft rock made of carbon. Coal originates from the compressed, lithified remains of dead leaves, stems and trunks of plants that grew in a swampy environment.
Contact metamorphism
metamorphism caused by heat from a nearby igneous intrusion. Contact metamorphic rocks are generally not foliated.
Continuous series
Because the plagioclase minerals maintain the same basic crystal structure but change continuously in their content of calcium and sodium, the right side of the diagram is called the continuous series.
Crystal habit
the way a mineral has grown by means of regular additions of ions to its surfaces from a liquid solution, a gas or molten rock.
Density
Its mass per unit volume (density=mass/volume). Density is a reflection of the relative “heaviness” of a mineral
Diorite
A relatively coarse-grained intrusive rock containing less silica than granite or granodiorite. It is composed primarily of plagioclase feldspar.
Discontinuous series
The left side of the diagram depicts reactions that result in minerals of distinctly different structure. It is therefore called the discontinuous series.
Dolomite
Either the magnesium-bearing carbonate mineral CaMg(CO3)2 or the rock that is composed largely of that mineral.
Evaporite
water-soluble, mineral sediments that result from the evaporation of bodies of surface water.
Extrusive igneous rock
mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff.
Feldspar
group of most common minerals of the Earth’s crust. All feldspars contain silicon, aluminum, and oxygen and may contain potassium, calcium and sodium.
Ferromagnesian silicate mineral
iron/magnesium bearing mineral, such as augite, hornblende, olivine or biotite.
Foliation
parallel alignment of textural and structural features of a rock.
Fractional crystallization
The separation of components of a cooling magma by sequential formation of particular mineral crystals at progressively lower temperatures.
Gabbro
dark, coarse-grained, intrusive igneous rock chemically equivalent to basalt.
Garnet
metamorphic index mineral. Forms at middle to high temperatures and pressures.
Gneiss
course-grained metamorphic rocks. Its often dramatic foliation results when high pressure segregates minerals into bands rich in quartz, feldspar, biotite, or hornblende.
Granite
a silica-rich, relatively light-colored intrusive rock.
Granodiorite
quartz-bearing igneous rock in which plagioclase is the dominant feldspar mineral.
Greenstone
a dark-green metamorphic rock. Except for a relatively few scattered larger crystals, most of the mineral components cannot be seen without magnification. Greenstones are formed during low-grade metamorphism of basaltic rocks.
Gypsum
a soft, hydrous calcium sulfate (CaSO4 - 2H2O) that occurs as several varieties.
Halite
(NaCl) is easily recognized by its salty taste and the fact that it crystallizes and cleaves to form cubes, as shown in the left-hand specimen in Figure 4-16.
Hardness
in minerals, hardness is gauged by which materials scratch which materials, or are scratched in return.
Hornblende
a black amphibole with a shiny luster. Hornblende is a silicate mineral that is common in rocks that form at high temperatures such as granite, diorite, or amphibolite.
Hornfels
a type of hard metamorphic rock created by the heat of contact metamorphism. The protolith of hornfels was typically a fine-grained sedimentary or volcanic rock. (Such as shale).
Igneous rock
rocks that form from magma, lava or tephra.
Intrusive igneous rock
body of igneous rock that has crystallized from molten magma below the surface of the Earth.
Lava
molten rock expelled by a volcano during an eruption.
Lithification
the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock.
Luster
the manner in which the surface of a solid reflects light.
Mafic silicate
ferromagnesian mineral
Magma
molten rock that is a mixture of molten silicates and gases.
Marble
limestone that has been metamorphosed. Under pressure, all of the calcite in the original limestone is recrystallized. Any vestige of fossils in the limestone is eradicated. Note that there is no chemical change: Calcite (CaCO3) is the principal mineral in both limestone and marble.
Metamorphic index material
form under specific temperature and pressure conditions. Geologists use them to determine the growth history of ancient mountain regions, even where only deeply buried “mountain roots” remain.
Metamorphic rock
rock that forms by recrystallization of a pre-existing rock due to changes in temperature, pressure, or fluids in the rock.
Metamorphism
the process that create metamorphic rocks.
Mica
silicate minerals easily recognized by their perfect and conspicuous cleavage along a single pane.
Micrite
exceptionally fine-grained carbonate mud.
Mineral
A naturally occurring element or compound formed by inorganic processes that has a definite chemical composition or range of compositions, as well as a distinctive properties and form that reflect its characteristic atomic structure.
Nonsilicate mineral
They do not contain the silicon-oxygen structures that characterize silicate minerals.
Nonfoliated metamorphic rocks
Non-foliated metamorphic rocks are formed from mineral grains lacking any particular alignment. Such random arrangement of minerals occurs during metamorphism in two ways. First, when rocks are exposed to elevated temperatures – in the absence of any directed forces – mineral grains are free to grow with any orientation. Thus, non-foliated rocks are always produced by lithostatic pressure. However, non-foliated rocks can also form in another way. If the precursor rock consists of equant sized grains – grains with shapes that have similar lengths, widths, and heights – then the application of directed force fails to produce any preferential orientation. Thus, rocks containing largely spherical or cubical shaped grains will not produce a foliated texture, no matter the intensity of the directed pressure.
Obsidian
an extrusive rock that cools too fast to form even small crystals. The magma that forms obsidian quickly solidifies to form a natural glass (Fig. 4-23). Obsidian forms from lavas that have lost most of their dissolved gasses, so it does not contain bubbles.
Olivine
this glassy looking iron and magnesian silicate often has an olive green color ( Fig 4-14). It is present in dark rocks such as basalt
Ooid
spherical grains formed by the precipitation of carbonate around a nucleus.
Oolite
Limestone made of ooids.
Partial melting
Occurs when rock that is subjected to high temperature and pressure is only partially melted and the liquid component moves to another location.
Phyllite
regional metamorphic rock similar to slate except that the foliation surfaces are shinier and more wrinkled. Forms at slightly higher metamorphic grade (higher temperature) than slate.
Pluton
having to do with intrusion of magma within the earth. Also called intrusive. Contrasts with volcanic, which has to do with extrusions of magma onto the earth’s surface as lava or tephra.
Plutonic igneous rock
rocks that form from intrusions of magma within the earth. Examples include granite and gabbro. Plutonic rocks are a sub-category of igneous rocks.
Porphyritic texture
Rock that is porphyritic, containing large and small crystals, or, in mining, a specific deposit containing widely disseminated metals, typically copper.
Pumice
White or creamy white highly vesicular rock, weathers to a pale brown on its surface. Very low density.
Quartz
a very common mineral that is relatively hard and tends to fracture like broken glass. Quartz is a silicate mineral, made of the elements silicon and oxygen.
Regional metamorphism
metamorphism in which a large volume of crust is subjected to stress and heat, forming foliated metamorphic rocks.
Rhyolite
felsic volcanic rock that originates as a lava flow. Rhyolite commonly has a white or pink color. Rhyolite comes from magma that originates in the crust.
Schist
regional metamorphic rock with foliation that is due to parallel flat minerals, especially mica minerals such as biotite or muscovite, with crystals big enough to see with the naked eye.
Sedimentary rock
rocks that form from accumulated sediment.
Sillimanite
indicates the highest level of temperature and pressure.
Slate
the regional metamorphism of shale. (the foliation is microscopic and is caused by the parallel alignment of minute flakes of silicates such as mica.
Strata
changes in conditions of deposition that cause materials of somewhat different composition or particle size to be deposited for a period of time. Sediment is deposited in layers that are originally horizontal.
Streak
color of a mineral when it is ground to powder.h
Texture
refers to the size and shape of individual grains and their arrangement in the rock.
Tuff
A rock formed of compacted volcanic fragments, some of which can be distinguished by the naked eye. If the fragments are larger than the rock grades into an agglomerate.
Vesicles
lava contains dissolved gases, bubbles will form small cavities
