Minerals naturally occurring; non living; solid that has a definite composition and structure
4000 different minerals naturally occurring- not made by man inorganic- not alive, never was alive, didn’t come from living materials
definite structure- atoms arranged in repeating patterns
definite composition- specific chemical formulabarite (BaSO4)
talc [Mg3Si4O10(OH)2]
2 Main Composition Groups silicates
(largest group) -Si & -O
non-silicates carbonates -CO3
oxides -Osulfides -Shalides -Cl or -F
sulfates -SO4
native elements not combined with any other atom
Crystal SystemsAtoms arranged in repeating patterns
Not all samples show flat sides and sharp edges, it depends on where and conditions of the sample when it formed
Constrictive environment creates small crystals, or masses of interlocking crystals
Not restrictive environment allows crystals to grow large
How Minerals Form 1. Cooling of hot magma (hot melted
rock)
2. Liquids containing the mineral evaporates, leaving the mineral
6 Major Crystal Systems 1. Cubic- (halite)
2. Orthorhombic- (sulfur)
3. Tetragonal
4. Monoclinic- (gypsum)
5. Hexagonal- (quartz)
6. Triclinic why 6?
Lengths of the axis and the angles at which the axis intersect determines the crystal system
Physical Properties Unique properties or descriptions that help to identify minerals
Hardness Luster Color Streak Cleavage vs. Fracture Specific Gravity Special properties
HardnessHow easily a mineral can be scratched
Mohs Hardness Scale-------------------Tools
1. talc2. gypsum 2.5 fingernail*3. calcite 3.5 copper penny*4. fluorite 4.5 iron nail5. apatite 5.5 glass plate*6. feldspar 6.5 steel file7. quartz 7.0 streak plate*8. topaz 9. corundum * tools we will use in lab. 10. diamond to determine a mineral’s
hardnessA higher number mineral will scratch a lower number mineral
Luster
How light is reflected from a mineral metallic—shines like a metal nonmetallic—does not shine like a metal
can be dull, pearly, glassy, silky, brilliant
ColorLook at mineral to recognize the color Usually a bad way to identify minerals, because most minerals can be different colors
sulfur, olivine, orthoclase, malechite, copper
Streakthe color of the mineral in powder form Use streak plate for minerals with hardness less than 7!
Cleavage Tendency for a mineral to break along smooth flat surfaces Why?
Orderly arrangement of atoms causes a weakness where bonds aren’t as strong. Relates chemical makeup and chemical structure
Cleavage is expressed in number of directions of cleavage & the angles at which they intersect
Directions of Cleavage1 direction—sheets of paper
2 directions—a box with open top and bottom
3 directions—a brick Can have more than three, but it is difficult to see except in a fluorite octahedral
Angles of CleavageAngles between the directions of cleavage are either 90o or NOT 90o Also described as perfect (easy to see) or poor (hard to see)
Fracture curved, broken of jagged edges without flat surfaces
special type of fracture—conchoidal fracture looks like a shell with curved pattern seen in quartz
Specific Gravity Mass per unit of volume compared to H2O (density of mineral compared to the density of water)It is heavy for it’s size??
Special Properties Optical properties- transparent or translucent
double refraction of calcite
Reaction to acid- members of the carbonate group fizz when put into acid…CO2 gas bubbles
ex. calcite, malachite
Magnetism- some minerals are magnetic, others are attracted to a magnet
ex. magnetite
Tasteex. halite is “salty”