Properties of Minerals

What is a Mineral? Minerals are formed in nature. Minerals are solids. Minerals have a crystalline, geometric structure. Minerals are inorganic; not made from a living thing.

Major Properties Color: come in many different colors Luster: the way a surface reflects light Streak: the color of a mineral in powder form Cleavage: the tendency of a mineral to break along flat surfaces Fracture: the tendency of a mineral to break unevenly along curved or irregular surfaces Hardness: a mineral’s resistance to being scratched Density: ratio of mass to volume

Impurities and other factors can give minerals their color These minerals are ALL forms of quartz! Color is not a reliable way to describe minerals.

Exposure to weather or chemicals may change the color of minerals. Color is not a reliable property to use in the identification of minerals! Oxidation turns iron from silver to black to red! Pyrite turns grey and black. Copper turns green!

Amethyst $68.00 Tanzanite $ Sapphire $ Diamond $3, Moissanite $349.oo REAL Gold

Luster plastic, dull, metallic, waxy, pearly, glassy, silky pearlywaxymetallic dullglassy, vitreousresinous, plasticsilky, fibrous

Streak Powder made from rubbing a mineral across a streak plate Pyrite Galena Hematite

Cleavage Minerals that break along even lines have cleavage.

Types of Cleavage

Fracture break along curved or irregular surfaces Conchoidal, “shell-shaped”fibrous irregular

Hardness Hardness can be measured using a scratch test: using Mohs Hardness Scale, which compares minerals to each other using common items such as a fingernail, copper penny, steel knife blade, glass A fingernail can scratch talc. Quartz can scratch glass, but fluorite cannot.

Density How much matter there is in a given space Density = Mass divided by Volume volumemass

Special Properties Magnetism Radioactivity Chemical Reaction Fluorescence Salty Taste But NEVER taste things in the lab! Double Image