3.5 - 4.0 on the Mohs scale.

Namibia, Zaire, Japan, Australia, Mexico, Bolivia, Chile, Germany, Hungary, England and the United States (Pennsylvania, Tennessee, Michigan (Keweenaw, Houghton and Ontanogon Counties) and the Western states).

Commonly called "ruby copper", cuprite is a secondary ore of copper that occasionally forms attractive ruby-like transparent crystals. Cuprite has a high refractive index which is even greater than diamond. Because of this, cuprite has a semi-metallic lustre and in the right lighting can be confused with hematite. If not for it's lustre, cuprite could also be easily be confused with pyrope garnet. Because of their softness, these are considered collectors gemstones and not suitable for use in jewelry which is subject to wear.

Transparent cuprite is not known to be enhanced. Opaque cuprite is occasionally coated with colorless wax, or rarely impregnated with plastic and/or other hardened agents to improve durabilty and appearance.

More information on gemstone enhancements.