Crocoite
By Bob Farrar
by Bob Farrar
The Mineral of the Month for November is crocoite.
Named from the Greek word crocon, for saffron, due to its color, crocoite is a beautiful mineral and a favorite among collectors.
Crocoite consists of lead chromate, PbCrO4. It crystalizes in the monoclinic system, and typically forms prismatic (long and slender) or acicular (needle-like) crystals. Its most distinctive characteristic is its color, typically brilliant orange to orange-red. It is rather brittle, so care must be taken in handling crocoite. Other physical properties include a hardness of 2.5 to 3.0, a specific gravity of 5.9 to 6.1, and poor cleavage. Color and crystal form are generally sufficient to distinguish crocoite.
Crocoite occurs in the weathered zones of lead deposits in the presence of chromium-bearing rocks. Neither lead nor chromium are particularly rare, but they tend to occur in different geological settings, which makes crocoite rare. By far the most important locality for crocoite is Dundas, Tasmania. There crystals up to 6 inches long have been found, along with great numbers of lesser specimens. The Red Lead Mine and the Adelaide Mine are particularly famous Tasmanian localities. The type locality of crocoite, however, is in the Ural Mountains of Russia. Callenberg, Saxony, Germany is another well-known locality. Other worldwide localities include Brazil, the Philippines, and Zimbabwe. U.S. localities are not as well known, but they include the Mammoth Mine in Tiger, AZ, the Darwin Mine in Inyo Co., CA, and the Eldorado Mine in Riverside Co., CA.
The rarity and beauty of good crocoite specimens makes them highly prized by collectors. Larger specimens, as might be expected, can be quite expensive. However, thanks mainly to the rich deposits of Tasmania, there are enough more modest specimens on the market that most serious collectors can add crocoite to their collections.
The Mineral of the Month for November is crocoite.
Named from the Greek word crocon, for saffron, due to its color, crocoite is a beautiful mineral and a favorite among collectors.
Crocoite consists of lead chromate, PbCrO4. It crystalizes in the monoclinic system, and typically forms prismatic (long and slender) or acicular (needle-like) crystals. Its most distinctive characteristic is its color, typically brilliant orange to orange-red. It is rather brittle, so care must be taken in handling crocoite. Other physical properties include a hardness of 2.5 to 3.0, a specific gravity of 5.9 to 6.1, and poor cleavage. Color and crystal form are generally sufficient to distinguish crocoite.
Crocoite occurs in the weathered zones of lead deposits in the presence of chromium-bearing rocks. Neither lead nor chromium are particularly rare, but they tend to occur in different geological settings, which makes crocoite rare. By far the most important locality for crocoite is Dundas, Tasmania. There crystals up to 6 inches long have been found, along with great numbers of lesser specimens. The Red Lead Mine and the Adelaide Mine are particularly famous Tasmanian localities. The type locality of crocoite, however, is in the Ural Mountains of Russia. Callenberg, Saxony, Germany is another well-known locality. Other worldwide localities include Brazil, the Philippines, and Zimbabwe. U.S. localities are not as well known, but they include the Mammoth Mine in Tiger, AZ, the Darwin Mine in Inyo Co., CA, and the Eldorado Mine in Riverside Co., CA.
The rarity and beauty of good crocoite specimens makes them highly prized by collectors. Larger specimens, as might be expected, can be quite expensive. However, thanks mainly to the rich deposits of Tasmania, there are enough more modest specimens on the market that most serious collectors can add crocoite to their collections.
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