Witch Eye Rhyolite tumbled stones from Scotland (new in 2021)

The igneous rock rhyolite or liparite is an effluent rock having a felsic composition, defined as greater than 68% silica. The name rhyolite is derived from Greek rhyx “lava flow”. Rhyolite has small crystals due to the extrusive formation of the rock. In outgrowth rocks, the magma (and from then on called lava) that reaches the Earth's surface cools quickly to very quickly, leaving no time for the minerals to develop large crystals. Rhyolite usually consists of the minerals quartz, potassium feldspar and plagioclase. Traces of more mafic minerals such as biotite, amphibole and pyroxene may be present in rhyolites. Due to the high silica percentage in rhyolite, the molten rock is very viscous (viscous). As a result, lava flows with a rhyolite composition will be much less mobile than the low-viscous mafic and therefore fast-flowing basalts. When rhyolite cools so quickly that it cannot form any crystals at all, it is called a vitropher or volcanic glass. The best-known variant of this is obsidian. Rhyolites are found everywhere where highly viscous magma can reach the earth's surface despite the viscous nature and solidify quickly. The deeper variants of rhyolite are the gangue granophyre and the deep rock granite. Rhyolite, also called koga in Japanese, is found in hills of the Scottish Glen Coe valley such as the Buachaille Etive Mòr, in Niijima, Japan and the Italian Lipari. Rhyolite volcanoes are also found on New Zealand's North Island and Iceland. Due to its mineral composition, rhyolite is often light in color. This color can also vary, from white through pink to light green. Rhyolite has a very bright color in the landscape as long as it receives a spark of light, sometimes so bright that it seems as if it is emitting light. Nice examples of this can be found on Landmannalaugar, an area in Iceland.