Volk Island (Volkostrov), Medvezhyegorsky District, Republic of Karelia, Russiai

Regional Level Types
Volk Island (Volkostrov)	Island
Medvezhyegorsky District	District
Republic of Karelia	Republic
Russia	Country

Island in the Lake Onega, located 1 km north of Kizhi Island.

The discovery of the amethyst occurrence on the island in 1798 is attributed to Adam V. Armstrong, when he was member of the management team of the Petrozavodsk cannon foundry. The best specimens of his amethyst collection are presently on display at the Mining Museum in Saint-Petersburg.

The amethyst occurrence is confined to the zone of a tectonic fault, in diabases and shungite-bearing shales of Lower Proterozoic age. Mineralised fissures and quartz-amethyst veinlets 0.5-4 cm thick have been observed at the outcrop of shungite-bearing shales. However, most of amethyst findings are related to the rocky debris in surface sediments. This debris is represented by silicified and partly limonitised rocks with quartz-amethyst veinlets and geodic cavities filled with crystals of smoky quartz, amethyst, acicular goethite, rare calcite and scaly hematite.

At the beginning of the 19th century, specimens of amethyst from Volk Island reached some European mineralogists/naturalists. The first description of the black and yellow-brown hair-like inclusions in amethyst was published in 1802 in Brünn (Brno) in the Patriotisches Tageblatt by Christian Carl André. For this mineral was proposed the name onegite, after Lake Onega in which the island is located. Later, due to a new description of the acicular inclusions given by Alexandre Foullon (1812), the name foullonite or fullonite was used particularly in France for a certain time. Vasily Severgin showed that the acicular mineral is an iron oxide-hydroxide (Severguine, 1827) and, consequently, the mineral was classified as goethite.

Rare small crystals of chalcopyrite, pyrite and a green uranium mica were observed by Gustav Rose on some amethyst specimens of the Foullon collection (Rose, 1837).

Fossils

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References