File:Copper (Mesoproterozoic, 1.05-1.06 Ga; White Pine Mine, Ontonagon County, Michigan, USA) 1 (16673131054).jpg

Copper from the Precambrian of Michigan, USA. (public display, Colorado School of Mines Geology Museum, Golden, Colorado, USA)

A mineral is a naturally-occurring, solid, inorganic, crystalline substrance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 4900 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

Elements are fundamental substances of matter - matter that is composed of the same types of atoms. At present, 118 elements are known (four of them are still unnamed). Of these, 98 occur naturally on Earth (hydrogen to californium). Most of these occur in rocks & minerals, although some occur in very small, trace amounts. Only some elements occur in their native elemental state as minerals.

To find a native element in nature, it must be relatively non-reactive and there must be some concentration process. Metallic, semimetallic (metalloid), and nonmetallic elements are known in their native state as minerals.

Copper is the only metallic element that has a "reddish" color - it’s actually a metallic orange color. Most metallic elements, apart from gold & copper, are silvery-gray colored. Copper tends to form sharp-edged, irregular, twisted masses of moderately high density. It is moderately soft, but is extremely difficult to break. It has no cleavage and has a distinctive hackly fracture.

The copper mass shown above comes from northern Michigan's White Pine Mine, which is developed in the Mesoproterozoic-aged Nonesuch Shale (~1.07 to 1.08 Ga). Native copper fills fractures in the Nonesuch Shale - the above specimen is an irregularly planar sheet of copper from such a fracture (the black material is the shale host rock). White Pine Mine copper mineralization occurred at 1.05 to 1.06 billion years ago.