Earth Minerals http://www.aqd.nps.gov/grd/usgsnps/rxmin/content.html

Minerals Crystalline solid Pure substance Found in nature Inorganic

Rocks Solid aggregate of minerals (mixtures)

Physical Properties Color Luster Cleavage Hardness Streak Crystal Form Specific Gravity Special Properties

Color Most obvious characteristic of minerals Most unreliable characteristic for identifying minerals Impurities cause color variations Example: Quartz

Luster Appearance or quality of light reflected from the surface of the mineral Descriptions: Metallic – look like metal regardless of color

Cleavage A minerals tendency to break along flat surfaces Depends on the type of bond used during the formation of mineral Fracture – minerals that break unevenly into curved or irregular pieces How to test: break the mineral

Hardness Measure of minerals ability to resist scratching Does not mean resistance to cleavage or fracture Hardest mineral – diamond Hardest common mineral – quartz Softest common mineral - talc How to test – rub mineral along a glass slide to see if it scratches the glass or not

Streak Color of a mineral in its powdered form More reliable indication of mineral color How to test: rub mineral against streak plate

Crystal Form External expression of a mineral’s internal orderly arrangement of atoms How crystals will grow without interference

Specific Gravity How dense a mineral is compared to water Minerals denser than water have a density greater than 1 Quartz, feldspar, calcite, and talc – 3 specific gravity Hematite and magnetite – 5 specific gravity Gold – specific gravity – 19.3 when pure Minerals less dense than water have a density below 1

Specific gravity… weight of sample in air loss of weight in water

Special Properties Magnetic – Magnetite – most common magnetic mineral Lodestone – type of magnetite that acts like a magnet

Fizzes with acid: Calcite will fizz when hydrochloric acid is placed on the sample The fizz produces carbon dioxide gas CO2

Taste: Mineral will have a particular taste like salt How do you test – lick it

Fluorescence Minerals absorb ultraviolet light and then produce visible light of various colors Calcite appears white but under UV light appears red

Odor – Minerals that smell Sphalerite – rich in zinc How to test – scratch the mineral and smell

Double Refraction – Light rays that bend as they pass through the mineral When the light bends it splits into 2 rays and produces a double image

Mineral ID practice… What is…? 1. 2. 3.

How Crystalline Minerals Form Evaporation of solutions Halite and Gypsum Cooling of melted substances Quartz and Olivine