일반명 : 자연동(Native Copper)

학명 : Copper Crystal

광산명 : Ray Min

Dims : 2.4x2.3x2.2cm

Loc : Pinal County, Arizona, U.S.A.

This hand specimen consists of an arborescent native Copper formation. It is in good condition, showing subtle damage if any, and contains warped Copper crystals that do not exceed 0.2-0.3" (5-8 mm) in length. Even though they are warped, one can see evidence of Spinel-law twinning in some spots. Each surface has a dull, pale green oxide coating surrounding it. There is no base or host rock present.

NATIVE COPPER

• Chemistry: Cu, Elemental Copper

• Class: Elements

• Group: Gold

• Uses: Minor ore of copper, ornamental stone

Native copper (copper found in a chemically uncombined state) has been mined for centuries and now is all but depleted as an economically viable ore. Other copper minerals are far more economical to mine and purify into metallic copper that is used for wiring, electrical components, pennies and other coins, tubing and many other applications. Native copper is still found in limited quantities in once-active mining regions. These finds are now valuable as minerological specimens and ornamental pieces. Fine specimens only rarely demonstrate crystal faces and these are prized above otherwise similar specimens.

PHYSICAL CHARACTERISTICS:

• Color is copper colored with weathered specimens tarnished green.

• Luster is metallic.

• Transparency is opaque.

• Crystal System is isometric; 4/m bar 3 2/m

• Crystal Habits include massive, wires and arborescent or branching forms as the most common, whole individual crystals are extremely rare but when present are usually cubes and octahedrons. Occasionally, massive forms will show some recognizable crystal faces on outer surfaces.

• Cleavage is absent.

• Fracture is jagged.

• Streak is reddish copper color.

• Hardness is 2.5-3

• Specific Gravity is 8.9+ (above average for metallic)

• Associated Minerals are silver, calcite, malachite and other secondary copper minerals.

• Other Characteristics: ductile, malleable and sectile, meaning it can be pounded into other shapes, stretched into a wire and cut into slices.

• Notable Occurrences include Michigan and Arizona, USA; Germany; Russia and Australia.

• Best Field Indicators are color, ductility and crystal habit.