silicified+tuff

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• Stone Age — the period in the history of humankind, preceding the Bronze Age and the Iron Age, and marked by the use of stone implements and weapons: subdivided into the Paleolithic, Mesolithic, and Neolithic periods. [1860 65] * * * First known period of… …   Universalium

• porcellanite — ▪ rock also spelled  porcelanite        hard, dense rock that takes its name from its resemblance to unglazed porcelain. Frequently porcellanite is an impure variety of chert containing clay and calcareous matter; when of this nature it is… …   Universalium

• Geology of the Australian Capital Territory — Australia grew around three fused pieces of very ancient continental crust (cratons). The geology of the Australian Capital Territory includes rocks dating from the Ordovician around 480 million years ago, whilst most rocks are from the Silurian …   Wikipedia

• Spherulite — Spherulites, in petrology, are small, rounded bodies that commonly occur in vitreous igneous rocks. They are often visible in specimens of obsidian, pitchstone and rhyolite as globules about the size of millet seed or rice grain, with a duller… …   Wikipedia

• Lesbos Island — Infobox Greek Isles name = Lesbos native name = Λέσβος skyline = Olympos lesbos.jpg sky caption = Olympos peak rises 968 meters over Lesbos coordinates = coord|39|10|N|26|20|E chain = North Aegean isles = 16 area = 1632.819 highest mount =… …   Wikipedia

• Orbicular jasper — from Madagascar Orbicular jasper is a variety of jasper which contains variably colored orbs or spherical inclusions or zones. In highly silicified rhyolite or tuff, quartz and feldspar crystallize in radial aggregates of needle like crystals… …   Wikipedia

• Uranium mining in Colorado — Uranium mining in Colorado, United States, goes back to 1872, when pitchblende ore was taken from gold mines near Central City, Colorado. The Colorado uranium industry has seen booms and busts, but continues to this day. Not counting byproduct… …   Wikipedia