Cuprite

Named for the Latin cuprum, "copper", in allusion to its copper content. It can form as bright transparent red crystals, or as lustrous, submetallic opaque crystals. Even the opaque form will have slightly red edges and faint transparency upon backlighting. Cuprite is often associated together with Native Copper in copper deposits, and frequently forms as an encrusting reddish coating over the Copper. Malachite is known to fully or partially coat a layer or pseudomorph over Cuprite, forming an interestingly shaped and a sometimes-sparkling green crystal form.