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Russian Gemstones Encyclopedia

Vladimir Bukanov. Russian Gemstones Encyclopedia

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

PUMPELLYITE


PUMPELLYITE (Pumpellyit—Pumpellyite—ѕумпеллиит) (Palache, C. & Vassar, H.E. 1925), after Raphael Pumpelly (1837-1923), a pioneer researcher of the detailed paragenesis of the copper minerals of the Keweenaw Penin., Michigan, the U.S.A., where the mineral was discovered.

Composition & Properties. Silicate – Ca2(Mg,Fe2+)(Al,Fe3+)2•[(OH)2•H2O|SiO4|Si2O7], subclass of diorthosilicates, monoclinic system. Hardness 5.5-6. Density 3.2. Glass luster. Perfect cleavage in one direction. Pumpellyite is found in the form of fine-needle crystals, usually forming radial-rayed or cryptocrystalline massive aggregates of chlorastrolite. Color: light blue, light bluish-green, sometimes brown. When polished, chlorastrolite displays the effect of cat’s-eyechlorastrolite cat’s-eye.

Deposits. Pumpellyite is formed under the conditions existing near the surface in metamorphic rocks and in the form of filling of amygdales in basalts. In Russia, ornamental pumpellyite was found in the North Urals, at the Turinskiy mine. In the Middle Urals, it was found at the Sarany deposit, and in skarn of the Blagodat’Mt. In the Krasnoyarsk Region pumpellyite was discovered at the Noril’sk region. In South Kyrgyzstan, at the Kanskoye deposit, they extracted rose pumpellyite. Its findings are also known in Germany – near Gissen, Hessen; and near Waldalgesheim, Rhineland-Palatinate; in Sweden – at the Långban mine, near Philipstad; in Romania – in the valley of the Lotru River in the South Carpathian Mts.; in South Africa – at the Witwatersrand mine; in New Zealand – at the North Range deposit, near Vakatipu Lake. In the U.S.A., pumpellyite was discovered in Michigan, on the Keweenaw Penin. and on the Isle Royal, Superior Lake. There, at the Cliff Cape deposit, it is found in amygdales of traps, in crystals up to 1x5 cm. Filling of amygdales is represented with massive chlorastrolite of green and yellow-brown color, and also with its green-light blue radial-rayed aggregates. In Canada, pumpel-lyite was discovered in Québec, at the Jeffrey mine; and in Ontario, at the Hemlo deposit they found vanadium-containing pumpellyite. It was found also in basalts of the Haiti Is. at the Limbe deposit.

Synonyms. Turtledove back | Chlorastrolite, from Gk. “chloros” – green, Lat. “aster” – star and Gk. “lithos” – a stone | Chlorozeolite, after the similarity with zeolite | Greenstone | Lotrite, after the discovery location in the Lotru Valley, Romania | Raystone | Green starstone | Isel Royale green stone | Lake Superior green stone | Zonochlorite.

Treatment. This mineral is easy polished, cut in cabochons, which size is usually not more than 1-2 cm. Pumpellyite is supposed to be a genuine American gemstone; in 1972, it was declared as a symbol of the Michigan State.

Similarity. Pumpellyite looks like epidote, clinozoisite and prehnite, which it is taken for, sometimes.

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