mineralogy

Vein quartz

If a channelway for hydrothermal solutions is left incompletely filled with mineral matter, there may be cavities, or “vugs” in the deposit which will be lined with inward pointing crystals. These are quartz crystals, showing mainly the pyramid (or, more exactly, rhombehedron) faces. The quartz was deposited on a rounded surface of hydrothermal hematite (Fe2O3)… Continue reading Vein quartz

mineralogy

A tale of two CaCO3’s — Calcite and Aragonite

Aragonite (left) and calcite (right), both CaCO3; image by author Here in this photo, we clearly have two different minerals–one aragonite and the other calcite. However, they both have the same chemical formula of CaCO3. So how can it be that these two different minerals are both calcium carbonate? Aragonite and calcite are polymorphs of… Continue reading A tale of two CaCO3’s — Calcite and Aragonite