Carnelian

Hardness: 6.5-7 on Mohs scale. Color: Translucent reddish-orange to brownish-red, sometimes with banding. Luster: Vitreous (glassy) to waxy. Crystal Structure: Trigonal (microcrystalline). Cleavage: None. Specific Gravity: 2.58-2.64.

Carnelian is a variety of chalcedony, which is a cryptocrystalline form of silica, consisting of very fine intergrowths of quartz and moganite. It forms at relatively low temperatures in volcanic and sedimentary rocks. The reddish-orange color is due to the presence of iron oxides (hematite). It can be found in amygdaloidal cavities of basaltic lavas, and also in sedimentary deposits such as gravels and weathered rock formations. Its formation can span various geological ages, often forming in secondary deposits.

Carnelian has been used for thousands of years as a gemstone and ornamental material. It is popular in jewelry (beads, cabochons, carvings) and as an inlay material. Ancient civilizations used it for seals, amulets, and signet rings. In modern times, it is still valued for its warm color and durability.

The name 'carnelian' is derived from the Latin word 'carnis,' meaning flesh, referring to its color. It was highly prized in ancient Egypt, Greece, and Rome. In the Bronze Age Minoan culture, carnelian was used to make decorative arts and seals. It is sometimes heat-treated to enhance its color, making lighter or browner material more vibrant. Banded varieties that resemble agate are often marketed as 'carnelian agate'.

In the field, carnelian can be identified by its reddish-orange to brownish-red color, translucent appearance, and waxy to vitreous luster. Its hardness (easily scratches glass but not steel file) is also a key identifier. It is commonly found in India, Brazil, Uruguay, Madagascar, and the United States (e.g., Oregon and Washington). Collectors often look for specimens with good saturation of color and minimal inclusions. Distinguishing it from natural reddish chalcedony may sometimes require closer examination or testing for iron oxide presence.