Aim: How can we identify minerals? Do Now: Define “inorganic” and give an example.

Describe 2 observations about the following minerals

How can we use color to identify minerals? 1. Color - Actual color, visible to the naked eye Easiest to use  not reliable halite and calcite Minerals can have the same color ex. halite and calcite Minerals can have more than one color ex. Quartz Some minerals have a characteristic color ex. Pyrite (fools gold) is usually a brassy yellow (goldish color) Quartz Pyrite

How can we identify the luster of a mineral? 2. Luster: the way light is reflected off the minerals surface Metallic – Its looks like a metal!!!! (very shiny) Nonmetallic – looks glassy, glossy, greasy, waxy, pearly, or earthy (doesn’t look like a metal)

How can we identify the streak of a mineral? 3. Streak: True Color of a mineral, in its powdered form when rubbed on a streak plate Usually a different color from the color of the mineral Pyrite  blackish streak Hematite  red-brown streak ***Excellent way to identify minerals***

How can we identify the hardness of a mineral? 4. Hardness: the resistance a mineral offers to being scratched (not broken) Done by scratching an unknown mineral with other substances whose hardness is known. Glass = hardness of 5.5 Mineral scratches glass = harder than 5.5 Mineral does not scratch glass = softer than 5.5. Mohs Hardness Scale

How can we determine if a mineral cleaves? 5. Cleavage: when a mineral breaks along flat or smooth surfaces due to the internal arrangement of atoms Mica – one direction (sheets) Halite – 3 directions (cubic) Calcite – 3 directions, not at 90° (rhombohedral) Feldspar – 2 directions at 90º

How can we determine if a mineral fractures? 6. Fracture: mineral breaks along uneven surfaces Does not follow the atomic arrangement Rough, chunky blocks, or pieces Quartz Sulfur Olivine

How can we use specific gravity (density) to identify a mineral? 7. Specific gravity – the density of a mineral compared to the density of water. Minerals differ in density All these physical properties are due to the Internal Arrangement of Atoms!!!!!!!!

Chemical Properties Used To Identify Minerals Acid test - mineral reacts with hydrochloric acid and bubbles ex. Calcite (CaCO3) Dolomite is a mineral that reacts with HCl only when it is in powdered form.

Other Useful Tests 1. Double Refraction: Calcite 2. Taste – Halite (salt) 4. Iridescences: Labradorite 3. Smell – Sulfur (rotten eggs) 5. Fluorescence: certain minerals "glow“ when exposed to ultraviolet light 6. Magnetism: use a magnet to determine if the mineral is magnetic - magnetite

Summary Describe the tests used to identify a mineral. How are cleavage and fracture different? Why is color not a reliable test for identifying a mineral? Describe the difference between metallic and non-metallic luster. What is the name of the mineral that has a hardness of 7, has fracture and a white streak? What mineral is usually identified by using the acid test? Explain what happens. Why is a streak a more reliable property than color in mineral identification?

What is the name of the mineral that is nonmetallic, has a hardness of 7, has fracture, many possible colors, and is used in jewelry? What is the name of the mineral that can be scratched by quartz and bubble with acid? What is the name of the mineral that has a hardness of 5.5, metallic luster and has a black streak and is used to make steel?

How do we test the physical property of minerals? Physical Properties of Minerals Identification Tests: Luster (metallic or non-metallic) Hardness (1-10) Cleavage or Fracture (How it breaks) Streak (color of powder) Density (specific gravity) Color (least reliable) These physical properties are due to the Internal Arrangement of Atoms!!!!!!!!