Mineral Guides

Quick answer: Cooling speed decides an igneous rock’s texture. Volcanic (extrusive) rocks such as basalt and obsidian cool quickly at

Quick answer: Evaporite minerals form when salty water evaporates and dissolved minerals crystallize out in order of solubility: carbonates first,

Quick answer: Contact metamorphism happens next to a hot magma intrusion: heat bakes the surrounding rock in a narrow zone,

Quick answer: Hydrothermal veins form when hot, mineral-rich water, heated by magma or deep burial, flows through cracks in rock

Quick answer: Charoite is a purple, swirling silicate mineral found in only one place on Earth: the Murun Massif near

Quick answer: Sodalite and lapis lazuli are both deep blue but are different materials. Lapis lazuli is a rock made

Quick answer: Rhodochrosite is manganese carbonate, colored pink to red by manganese. Banded pink rhodochrosite comes famously from stalactites in

Quick answer: Kyanite is an aluminum silicate whose hardness changes with direction: about 4.5 to 5 along the length of

Quick answer: Diamond and graphite are both pure carbon; the difference is how the atoms are arranged. In diamond, each

Quick answer: Galena is lead sulfide (PbS), the world’s main ore of lead and often an important source of silver.