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.

Mineral Properties Colour: minerals come in many different colours Lustre: the way a surface reflects light / how shiny is it? Streak: the colour 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

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

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

Colour Amethyst $68.00 Tanzanite $720.00 Sapphire $500.00 Diamond $3,000.00 Moissanite $349.oo REAL Gold

Lustre plastic, dull, metallic, waxy, pearly, glassy, silky waxy glassy, vitreous resinous, plastic silky, fibrous

Streak Colour of the powder made from rubbing a mineral across a streak plate Some paints are based on powdered minerals Galena Pyrite Hematite

Mineral Cleavage & Fracture Some minerals split along flat surfaces when struck hard--this is called mineral cleavage Other minerals break unevenly along rough or curved surfaces--this is called fracture A few minerals have both cleavage and fracture

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 is the ability to scratch another mineral Mohs Hardness Scale compares minerals to each other from 1 (talc) to 10 (diamond) using a scratch test Quartz (most common mineral and most dust particles) is 7 A fingernail can scratch talc. Quartz can scratch glass, but fluorite cannot.

Density Density tells us how much matter there is in a given space Density = Mass divided by Volume Some minerals are very dense eg. galena, magnetite and gold volume mass

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