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Geology Lab Chapter 2

Terms

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igneous rock
Created from cooled magma
flourescent
minerals grow when exposed to ultraviolet light. Caused by impurities in the mineral called activators, which respond by giving off colored light
specific gravity
Ratio between mass of a mineral and the mass of an equal volume of water. Mass of mineral / volume of water displaced
diaphaneity
or transparency. A mineral's ability to transmit light. Can be transparent, translucent, milky, or opaque
mineral
Naturally occurring, inorganic solid with a definite chemical composition and internal molecular structure. Chemical composition and internal structure determine physical properties of mineral
tenacity
Resistance to breakage.
magma
Molten rock from the earth's interior, cools to form igneous rock
crystal form
External appearance of a perfectly formed crystal. The flat external surfaces are called crystal faces
rock cycle
Illustrates basic processes that form and destroy rocks near the earths surface
anhedral
Minerals that do not exhibit any crystal faces
taste
Halite tastes salty
precipitate
Crystallize. Dissolved substances crystallize, sediment settles to form sedimentary rock
luster
Appearance of light reflected through a mineral. Metallic and nonmetallic two basic types. Dull metallic = submetallic. Nonmetallic could be greasy, pearly, earthy, dull, resinous, silky, vitreous (like glass)
effervescing
bubbling
magnetism
Attraction of a mineral to a magnet. Some minerals, like magnetite, have high iron content and are attracted to magnets
subhedral
Exhibit some of their natural surfaces.
fracturing
Breaking of a mineral along a surface other than a plane of weakness. Conchoidal - break forming a smooth curved surface like broken glass (quartz and volcanic glass) Other types are splintery and irregular
montmorillonite
most expansive clay mineral, belongs to the silicate group and is a byproduct of rock weathering. Common in north-central Texas clay deposits
hardness
Mineral's resistance to abrasion (scratching). Mohs developed a standard of 10 minerals by which other minerals may be tested.
double refraction
occurs when light passing through a mineral splits into two rays, so an object viewed through the mineral has a double image. Calcite, for example
striations
Appear on cleavage faces of some minerals and look like straight, hairline grooves
smell
Sulfur smells like rotten eggs, talc may have a sweet smell
euhedral
A crystal that exhibits all of its natural crystal faces
color
Physical property of mineral, diagnostic of only a few minerals because the colors of different samples of the same mineral often vary
feel
I.e., talc feels soapy, halite may feel greasy
metamorphic rock
Created under influence of extremely high pressures and/or temperatures, and chemically active fluids, minerals in preexisting rocks may shift, grow, or react to form new minerals
physical properties
cleavage, crystal form, hardness, luster, specific gravity, streak
hydrochloric acid
HCl reacts with calcite (CaCO3) to create effervescent carbon dioxide gas
streak
Color of a mineral in powdered form. Obtained by rubbing the mineral on a piece of unglazed porcelain. More reliable than color for diagnosis.
cleavage plane
Flat surfaces or planes of weak chemical bonding between layers of atoms along which crystalline substances break.

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