MINERALS Reese
How do they form Minerals form when molten materials cools and hardens inside the Earth or on the surface. Sometimes minerals from when solutions with solutes evaporate.
MINERALS Occur naturally and are inorganic solids (not alive). Have crystalline structure.
MINERALS Chemically minerals are elements or compounds. Example: Gold is an element & a mineral. Example: NaCl is a compound & a mineral.
MINERALS Rocks are made up of two or more minerals. Example: Limestone is a rock made up minerals calcite & aragonite. Rocks can be minerals but not all minerals are rocks. Example: Cu is a mineral but is not a rock
MINERALS There are about 3,000 minerals on Earth.
BARITE
CARBON
QUARTZ
GRAPHITE
Copper
FLUORITE
MINERAL PROPERTIES
LUSTER The way a mineral’s surface reflects light.
LUSTER May vary from one sample to another sample of the same substance. Two major types of luster: Metallic Nonmetallic
Metallic Luster
Nonmetallic luster Earthy Luster Glassy
Nonmetallic Pearly Luster
COLOR Not very useful for identifying minerals whose color vary with the sample. Example: the colors of minerals quartz & fluorite vary with their samples. Quartz Fluorite
COLOR Useful only for those minerals which always have the same color or very unique colors. Example: Malachite– green azurite----- blue
SULFUR
Malachite
Azurite
STREAK Color of a mineral in it powdered form. Can be obtained by rubbing the mineral across a streak plate-- a piece of unglazed porcelain tile. Example: hematite always gives a reddish brown streak no matter what type of luster it displays.
Streak Examples Hematite leaves a reddish brown streak.
Streak Examples Pyrite leaves a greenish black streak.
HARDNESS Ability of a mineral to resist scratching. It is tested using the Mohs Hardness Scale.
Mohs Hardness Scale Based on the fact that a harder mineral will scratch a softer one. Ten minerals are numbered from softest to hardest. Talc is the softest & has a value of 1. Diamond, the hardest of all minerals, has a value of 10.
DENSITY Useful mineral identification property. Used to determine the identity and purity of minerals. Pure mineral density is a constant value. Density = mass/volume. Example: gold and pyrite appear similar. Pyrite is often called “fool’s gold”. You can tell the two minerals apart by comparing their densities. Gold’s density: 19.3 g/cc Pyrite’s density: 5.01 g/cc