Minerals

What is a mineral? A mineral is a naturally occurring, inorganic crystalline solid with a repeating structure and constant chemical composition. A mineral is a naturally occurring, inorganic crystalline solid with a repeating structure and constant chemical composition.

A mineral is/has naturally occurring (formed in nature) naturally occurring (formed in nature) inorganic inorganic solid solid a repeating structure a repeating structure definite, constant chemical composition definite, constant chemical composition (for example: NaCl – halite) (for example: NaCl – halite)

Minerals form by… cooling of magma or lava

or formed by… precipitation from a solution

Stalactites and Stalagmites

ore - a mineral-rich rock deposit containing usable amounts of metal that can be mined for a profit ore - a mineral-rich rock deposit containing usable amounts of metal that can be mined for a profit gem - rare beautiful mineral that is cut and polished and often sold for a large profit. gem - rare beautiful mineral that is cut and polished and often sold for a large profit.

Mineral Identification Chemical composition determines the various properties of a mineral. Chemical composition determines the various properties of a mineral. Minerals are grouped according to their chemical composition Minerals are grouped according to their chemical composition Minerals can have the same basic composition and can be very different. Minerals can have the same basic composition and can be very different.

Two Carbon Minerals… Graphite Silver Gray Silver Gray Soft Soft Metallic luster Metallic luster Black streak Black streak Opaque Opaque Diamond Cubic Crystalline Structure Transparent Very Hard Adamantine (very vitreous) No streak

7 Mineral Identifying Characteristics color – most easily observed, but least reliable color – most easily observed, but least reliable luster – the way a mineral shines in reflected light, either metallic (could be dull and still metallic-like a penny) or non- metallic (vitreous, pearly, earthy, glassy, greasy, waxy, resinous, oily & dull) luster – the way a mineral shines in reflected light, either metallic (could be dull and still metallic-like a penny) or non- metallic (vitreous, pearly, earthy, glassy, greasy, waxy, resinous, oily & dull)

Guess a luster...

streak – the color of a minerals powder after scratching it on a streak plate

hardness – a minerals resistance to being scratched (Moh’s hardness scale) Moh’s Hardness Scale 1 – talc 2 – gypsum2.5 – finger nail 3 – calcite3.5 – copper penny 4 – fluorite4.5 – steel nail 5 – apatite5.5 – glass plate 6 – feldspar 7 – quartz7.0 – streak plate 8 – topaz 9 – corundum 10 – diamond

fracture – when a mineral breaks along uneven surfaces (quartz – conchoidal) fracture – when a mineral breaks along uneven surfaces (quartz – conchoidal) cleavage – a minerals tendency to split along smooth flat surfaces cleavage – a minerals tendency to split along smooth flat surfaces

specific gravity – the ratio of the weight of the mineral to the weight of an equal volume of water (how heavy the mineral feels – hummm a little like density) specific gravity – the ratio of the weight of the mineral to the weight of an equal volume of water (how heavy the mineral feels – hummm a little like density)

Special Properties acid test – weak hydrochloric acid reacts with calcium-carbonate (CaCO 3 ), found in calcite & other minerals acid test – weak hydrochloric acid reacts with calcium-carbonate (CaCO 3 ), found in calcite & other minerals magnetism – the presence of iron-ore in minerals can be tested with a magnet, found in magnetite magnetism – the presence of iron-ore in minerals can be tested with a magnet, found in magnetite

Fluorescence – certain minerals glow under UV light due to the presence of manganese, found in fluorite, calcite, willemite, sphalerite and franklinite. Fluorescence – certain minerals glow under UV light due to the presence of manganese, found in fluorite, calcite, willemite, sphalerite and franklinite. Double Refraction – when a clear mineral displays two images placed on top, found in calcite. Double Refraction – when a clear mineral displays two images placed on top, found in calcite.