Curved Cuprite from Queensland

Mineral Matters #363

This week’s Facebook Mineral of the Week Group’s selected theme is crystals with curved habits.

I came across this one whilst preparing for a presentation later this week.

Cuprite forms in a few habits. Most often as cubes or octahedra, but sometimes as long thin crystals, often referred to as “chalcotrichite”). When they are particularly small, long and thin, they can be curved such as the one below.

Cuprite has is in the isometric (or cubic) class crystal structure, meaning its unit cell is shaped like a cube. However, as “chalcotrichite”, cuprite can preferentially grow along specific crystallographic directions. In this case, the growth is elongated along the [001] crystallographic axis, which is perpendicular to the cube faces. The curve is more to do with the small size!

Below: Cuprite (chalcotrichite), Mount Isa, Queensland. Width of view 9mm.