Natural Rhyolite — Rough

Rhyolite is an extrusive igneous rock with a felsic composition, the volcanic equivalent of granite. Its mineralogical formula is not fixed, being predominantly composed of quartz (SiO₂), alkali feldspars (KAlSi₃O₈) and plagioclase, with possible traces of biotite, hornblende and iron oxides. Its formation occurs by the rapid cooling of highly viscous, silica-rich lavas on the Earth's surface. The high viscosity makes it difficult for gases to escape, generating porous, brecciated textures or visible flow structures in the rock. The color varies between shades of gray, beige, pink, red and green, determined by the proportion of feldspars, iron oxides and secondary minerals present. Hardness: 6 to 7 on the Mohs scale. Density: 2.4 to 2.6 g/cm³. Crystalline system: variable (microcrystalline to amorphous structure). Available variations, approximate data: 1 to 3 cm — up to 0.025 kg — 40 pieces per kg 3 to 6 cm — 0.030 to 0.150 kg — 11 pieces per kg 6 to 15 cm — 0.150 to 0.800 kg — 2 to 3 pieces per kg