MINERALS
· Must occur naturally-can’t be manmade
· Can not be formed by organic processes
· Must be solid
· Must have specific chemical composition unique to each mineral-most
Minerals are compounds (chemical combination of 2 or more
Elements)
· Must have a definite crystalline structure-atoms are arranged in
Geometric shapes that repeat again and again, called crystals ex=cubic
Orthorhombic etc.
A mineral is a naturally occurring inorganic solid with specific chem. Composition and definite crystalline structure.
Classified by atomic arrangement (physical characteristics) and chemical composition.
Physical properties- due mainly to the internal arrangement of atoms.
Six key properties used
1.color-most visible property, not reliable on its own-too many
minerals appear to be the same color
2.streak-color of mineral in its powdered form-can be different
from color of mineral-reliable
3.luster-how the mineral reflects light-2 types- metallic and
nonmetallic. Metallic shines like metal, nonmetallic has no
metal shine could be dull, glossy, pearly, earthy, greasy etc.
4.hardness-the ability of a mineral to resist being scratched. Compared to Moh’s hardness scale of 10 minerals with predetermined hardnesses. Talc (1) is softest; diamond (10) is the hardest.
5.cleavage-tendency of a mineral to split along one or more flat
surfaces or planes. Many types of cleavage-Mica has cleavage
in one direction because its atoms are arranged to form sheets.
Halite is cubic it breaks into small cubes with 3-directional
cleavage.
6.fracture-mineral breaks unevenly.
Other physical properties include
Crystal shape- (or crystal habit) shape the mineral grows in nature-pyramids or fibers for example.
Double refraction- some minerals bend light in two directions when it is passed through them-like calcite
Iridescence-rainbow colors are produced when light reflects off mineral
Magnetic properties-behave like magnet
Electrical properties-good conductors of electrical currents-like some quartzes
Taste-dangerous, toxic, do not do!
Density-comparison of minerals with the same volume but different densities-how tightly packed the atoms are within an element.
Specific gravity-relative density of mineral compared to an equal volume of water at 4 C.
React with acid-mineral may bubble or effervesce when it comes in contact with dilute acid-ex-calcite