Minerals Typical minerals Copper – Used in electrical wiring Gold – Used for jewelry Talc – Baby powder Quartz – The main ingredient in glass A rock can be defined as an aggregate of two or more minerals, but there are some exceptions.
Earth Mineral An earth mineral is… Naturally occurring Inorganic Solid Possesses an orderly internal structure Has a definite chemical composition
Crystal Form External expression of a mineral’s orderly internal arrangement of atoms. Examples Pyrite – Cubic Quartz – Hexagonal
Luster The quality of light reflected from the surface of a mineral. Examples Galena - Metallic Fluorite – Non-metallic
Types of Luster Metallic The mineral is opaque and reflects light as a metal would. Submetallic The mineral is opaque and dull. The mineral is dark Nonmetallic minerals are described using modifiers that refer to commonly known qualities. Waxy The mineral looks like paraffin or wax. Vitreous The mineral looks like broken glass. Resinous The mineral looks like hardened tree sap.
Cleavage Tendency of a mineral to break along planes of bonding Fracture describes the quality of the cleavage surface. fibrous ( dull, silky) fracture conchoidal (curved, shell-like lines) fracture irregular (rough, jagged) fracture
Cleavage Types Cubic Cleaves in three directions at 90° to one another Rhombohedral Cleaves in three directions but not at 90° to one another Octahedral Cleaves in four directions Dodecahedral Cleaves in six directions Basal Cleaves in one direction Prismatic Cleaves in two directions
Specific Gravity Specific Gravity of a mineral is a comparison or ratio of the weight of the mineral to the weight of an equal amount of water. The weight of the equal amount of water is found by finding the difference between the weight of the mineral in air and the weight of the mineral in water. The most common is 2.5 – 3
Others Taste Only soluble minerals have a taste, but it is very important that minerals not be placed in the mouth or on the tongue. Feel Magnetism Magnetism is the characteristic that allows a mineral to attract or repel other magnetic materials. Reaction to Acid