Minerals in space group 224

Cuprite is an oxide mineral composed of copper(I) oxide Cu2O, and is a minor ore of copper. thumb|left|Cuprite from Tsumeb Mine (size:2.3 x 2.1 x 1.2 cm Its dark crystals with red internal reflections are in the isometric system hexoctahedral class, appearing as cubic, octahedral, or dodecahedral forms, or in combinations. Penetration twins frequently occur. In spite of its nice color, it is rarely used for jewelry because of its low Mohs hardness of 3.5 to 4. It has a relatively high specific gravity of 6.1, imperfect cleavage and is brittle to conchoidal fracture. The luster is sub-metallic