Carnelian

Hardness: 6.5-7 on the Mohs scale. Color: Translucent to opaque, typically reddish-brown to orange-red, but can also be found in other shades like yellow, white, grey, or black. Luster: Waxy to vitreous. Crystal Structure: Trigonal (cryptocrystalline quartz). Carnelian typically does not exhibit distinct cleavage.

Carnelian is a variety of chalcedony, which is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. Its reddish-brown color is due to the presence of iron oxides (hematite). It forms in a wide range of geological environments, often as secondary deposits in volcanic rocks, sedimentary rocks, or hydrothermal veins. It typically forms from low-temperature solutions filling cavities and fissures. Its geological age varies greatly depending on the specific deposit, ranging from relatively young to very ancient formations.

Primarily used as a gemstone in various forms of jewelry, including rings, pendants, beads, and carvings. Also used historically for seals, signet rings, and decorative objects. Its relatively good hardness and attractive color make it suitable for a variety of lapidary applications.

Carnelian has been used since ancient times for carving and jewelry. It was popular in ancient Egypt, Rome, and Greece, often associated with courage, vitality, and protection. It was also believed to prevent illness and promote peace. The name 'carnelian' is thought to derive from the Latin word 'caro' or 'carnis', meaning flesh, referring to its reddish-pink color.

In the field, carnelian can be identified by its distinctive reddish-brown to orange-red color, waxy to vitreous luster, and its hardness, which allows it to scratch glass. It often occurs as nodules or in veins. Commonly found in India (especially the Deccan Traps), Brazil, Uruguay, Madagascar, and parts of the United States. When collecting, look for well-formed nodules or pieces with vibrant, uniform color and good translucency. Avoid pieces with cracks or excessive inclusions. Note that some carnelian on the market may be heat-treated agate to enhance its color.