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Turquoise in the Sinai Peninsula is found in lower Carboniferous sandstones overlain by basalt flows and upper Carboniferous limestone. The overlying beds were presumably the source of the copper, which precipitated as turquoise in nodules, horizontal seams, or vertical joints in the sandstone beds.
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains, cemented together by another mineral. Sandstones comprise about 20–25% of all sedimentary rocks. [1] Most sandstone is composed of quartz or feldspar, because they are the most resistant minerals to the weathering processes at the Earth's ...
Bollingen Sandstone (also Buchberg Sandstone, Uznaberg Sandstone, Bollinger-Lehholz Sandstone and Güntliweid Sandstone): Rapperswil-Jona by the Upper Lake Zürich Grès à cailloux roulés : near Avenches
The site was rediscovered in 1809 by Ulrich Jasper Seetzen, and since then has seen several excavation teams, Richard Lepsius's excavation in 1845 being the first. Major C. K. McDonald's visits to the site, including residence at the site from 1854–1866 (and an effort to mine turquoise there) resulted in only surface finds (arrowheads and such) with no further excavation.
Chalcedony (/ k æ l ˈ s ɛ d ə n i / kal-SED-ə-nee or / ˈ k æ l s ə ˌ d oʊ n i / KAL-sə-doh-nee) [2] is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. [3]
It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt. The name opal is believed to be derived from the Sanskrit word upala , which means 'jewel', and later the Greek derivative opállios (ὀπάλλιος).
In North east Tasmania the Mathinna Group starts in the Ordovician with Stony Head Sandstone, a quartz sandstone formed in turbidity flows. Turquoise Bluff Slate formed from shale. Fossils are rare (mostly sparse graptolites), and ages hard to determine. [4] The Wurawina Supergroup formed in the Duck Creek Syncline amongst other places.
The lakes are renowned for their distinctive colours, ranging from turquoise to mint green, grey or blue. [5] Pannonian Basin ... Sandstone, marl, and limestone ...