Carnelian belongs to the quartz group of minerals, the second most abundant mineral group on earth. Carnelian is easily identified by its distinct orange to brown-red color, and its superior quartz hardness. Carnelian colors can range from yellowish orange to orange and from deep-red to brownish-red. Its distinctive color is owed to iron impurities and if heated, its color can be enhanced. Deep-red and reddish-orange colors are considered most desirable. Carnelian ranges in clarity from translucent to opaque. When held against the light, carnelian stones can exhibit an unevenly distributed transparency, often appearing cloudy. Carnelian has an attractive vitreous to wax-like luster when cut and polished.