because it started out as silica-rich magma, eventually erupting as a viscous surface lava flow. This molten earth origin is what classes rainbow obsidian as an igneous rock. Lava destined to ...

A solid crystal floats within the molten rock remaining. A portion of this partially crystallized / partially molten magma is then extruded, resulting in rapid cooling. The silica content of rocks is ...

Before we get into the snowflakes, obsidian is formed when rhyolitic magma (viscous molten rock with high concentrations of silica, but low levels of water and gas) quickly cools into a solid ...

a process known as slab melt. Adakites are silica-rich rocks characterised by high strontium-yttrium ratios and low yttrium and ytterbium content. The origin of adakites is unclear, with opinion ...