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The nodules are white with fine grey or black veins in an erratic, often web-like pattern, opaque with a sub-vitreous luster. The crystals at Iona are colorless, white or brown and are often translucent or transparent. Its structure is monoclinic with a Mohs hardness of 3.5 and lacks regular cleavage. Crystals are prismatic and flattened on ...
White veins in dark rock at Imperia, Italy. In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation. The hydraulic flow involved is usually due to hydrothermal circulation. [1]
The stone found in an old mine was called “belomorite” — because, as Fersman explains, “The White Sea shimmered with the colors of moonstone... or did the stone reflect the pale blue depths of the White Sea?..” — Geologists took several samples to the Peterhof lapidary factory , recommending it as a new jewelry stone. [3]
Supíkovice marble (supíkovický mramor) from Supíkovice, Jeseník District: grey-white; Marble mis-nomers: Cetechovice marble (cetechovický mramor) from Cetechovice, Kroměříž District: coloured [c] Karlík marble (karlický mramor), from Barrandien, Karlík, Prague-West District: black with gold-yellow-colour veins [d]
Most black obsidians contain nanoinclusions of magnetite, an iron oxide. [25] Very few samples of obsidian are nearly colorless. In some stones, the inclusion of small, white, radially clustered crystals (spherulites) of the mineral cristobalite in the black glass produce a blotchy or snowflake pattern (snowflake obsidian). Obsidian may contain ...
Mineralogically the occurrence is important because all three white mica phases are present in an equilibrium assemblage. [ 4 ] There are several theories regarding the formation of the chiastolite cross, however the most widely accepted theory, proposed by Frondel in 1934, suggests that there is a selective attachment of impurities at the ...
Novaculite, also called Arkansas Stone, is a microcrystalline to cryptocrystalline rock type that consists of silica in the form of chert or flint. It is commonly white to grey or black in color, with a specific gravity that ranges from 2.2 to 2.5. It is used in the production of sharpening stones.
Variscite has been used in Europe to make personal ornaments, especially beads, since Neolithic times. Its use continued during the Bronze Age and in Roman times although it was not until the 19th century that it was determined that all variscite used in Europe came from three sites in Spain, Gavá (Barcelona), Palazuelo de las Cuevas (Zamora), and Encinasola (Huelva).