Minerals Naturally formed Solid Inorganic Not man-made Solid Ice is a mineral, liquid water is not Inorganic Formed by inorganic processes Specific chemical composition Minerals are either chemical elements Gold and silver Or chemical compounds in which atom are present in specific ratios SiO2 – quartz Characteristic crystal structure regular, repetitive geometric patterns

Minerals Because minerals have a crystal structure, they are said to be crystalline Solids which do not possess a crystal structure are called amorphous solids and are not minerals glass

Identification of Minerals Properties of Minerals are determined by their compositions and crystal properties Primary diagnostic properties Determined by observation or performing a simple test Several physical properties are used to identify hand samples of minerals

Physical Properties of Minerals Crystal Habit or Form Geometric arrangement of planar faces that bound a crystal Habit or form is the external expression of a mineral that reflects the orderly internal arrangement of atoms Distinctive shape or outward appearance of a particular mineral pyrite

Physical Properties of Minerals Cleavage Tendency of a mineral to break in preferred directions along planes of weakness Mica, halite, calcite

Cleavage Calcite Halite Mica

Types of Cleavage

Physical Properties of Minerals Hardness Mineral’s resistance to scratching Governed by crystal structure and bond strength The stronger the bonds, the harder the mineral Mohs relative hardness scale Relative hardness values can be assigned by determining the ease or difficulty with which one mineral will scratch another Scale is divided into 10 steps Talc – 1 Diamond - 10

Moh’s Relative Scale of Hardness

Moh’s Relative Scale of Hardness

Physical Properties of Minerals Luster Quality and intensity of light reflected from a mineral Metallic Non-Metallic Vitreous – glassy Resinous Pearly Greasy

Luster Metallic Nonmetallic - pearly

Physical Properties of Minerals Color Not always a reliable means of identification Color is determined by chemical composition Corundum Ruby Sapphire

Physical Properties of Minerals Streak Thin layer of powdered mineral made by rubbing a specimen on a non-glazed fragment of porcelain

Physical Properties of Minerals Density Mass per unit volume (g/cm3) How light or heavy a mineral feels Galena has a high density

Other Physical Properties Taste Smell Reaction to HCL (calcite) Magnetism (magnetite) Feel