What is a Mineral? Naturally formed solid substance with a crystal structure

What do All Minerals have in Common? Formed by Natural Processes Are not Alive and Never Were Alive Have a Definite Volume & Shape Are Elements or Compounds with a Unique Chemical Make-Up Are Crystals (particles arranged in patterns that are repeated over and over)

How do Minerals Form?

Physical Properties Used to Identify Color – Can be misleading – Can vary due to impurities

Physical Properties Used to Identify Luster – Surface Reflection – Metallic = Shiny – Non-Metallic = Dull

Physical Properties Used to Identify Streak – The color of the powdered form of the mineral – The color of the streak can be different than the mineral – Minerals must be softer than the streak plate

Streak - Quartz Quartz comes in many colors, but… the streak is always white!

Physical Properties Used to Identify Hardness – A measure of how easily a mineral can be scratched Mohs Hardness Scale – 1 (Talc) = Softest – 10 (Diamond) = Hardest

Simple Hardness Test Method Test more than one area of each sample Fingernail: Hardness less than 2 Glass: Hardness = 5.5 If you can make a scratch in the mineral with your fingernail: – Hardness < 2. If you cannot make a scratch in the mineral with your fingernail, but the mineral cannot make a scratch in the glass: – 2 < Hardness < 5.5 If the mineral scratches the glass: – Hardness > 5.5

Physical Properties Used to Identify Cleavage and Fracture – Atomic arrangement determine the way the mineral breaks Cleavage: Minerals break along smooth, flat surfaces and every break has the same general shape Fracture: Minerals break with random, jagged edges

Mica Mica cleaves in thin sheets, because the weakest joints are between flat sheets of strongly-joined atoms.

Galena Galena cleaves into cubes, because the joints inside are equally strong.

Gold The “nugget” shape of gold is a good representation of random fracture.

Physical Properties Used to Identify Density – Reflects the atomic mass and structure of a material – If you had a sample of gold and a sample mica of the same size, the gold would have greater weight

Physical Properties Used to Identify Specific Gravity – the ratio of the mass of a substance to the mass of an equal volume of water at 4  C.

Physical Properties Used to Identify Magnetism – Minerals often have a strong or weak attraction to a magnetic field. Most magnetic minerals are opaque, metallic-looking minerals

Physical Properties Used to Identify Smell – Sulfides smell like a struck match or rotten eggs – Arsenic smells like garlic Taste – Halite and Hanksite are salty – Sylvite is bitter Texture – Fluorite has a smooth texture – Talc is greasy

Physical Properties Used to Identify Refractive Index – When light travels from one substance to another, it bends Fluorescence – Some minerals “glow” when exposed to black light

Groups of Minerals About 1,500 unique minerals have been identified Geologists have classified minerals into groups – Distinct Chemical Nature – Specific Characteristics

Groups of Minerals Silicates – Most abundant group – Contain Silicon and Oxygen – Strongly-bonded Tetrahedron Ions

Groups of Minerals Carbonates – Composed of one or more metallic elements combined with a Carbonate (CO 3 - ) – Typically transparent and lightly colored – A common component of the earth’s inner crust CalciteRhodochrosite

Groups of Minerals Oxides – Compounds of Oxygen and a Metal – Strong Chemical Bond – Very Hard and Dense – Great sources of iron and rare metals Hematite

Groups of Minerals Sulfides – Sulfur and a Metallic Ion – Highly symmetric, simple structures Low Hardness and High Specific Gravity GalenaPyrite

Groups of Minerals Sulfates – Composed of Elements with a Sulfate Ion (SO 4 2- ) – Delicate and occur near the earth’s surface BariteGypsum

Groups of Minerals Native Elements – Made up of a Single Element – Highly Ordered Atomic Arrangment CopperGold

What is a Gem? Mineral or rock that has value – Usually rare Example: – Mineral: Corundum – Gem: Ruby

Mineral Uses – Building a House

Mineral Uses – In the Kitchen

Mineral Uses – Transportation

Mineral Uses – Medical/Dental