Malachite and Hidden Collection

Mineral Matters #748

You probably know by now that my favourite colour is blue, but did you know I have a favourite crystal form? Well, actually two or three.

I like the shape of many crystals in the isometric (or cubic) crystal system, particularly octahedral or tetrahedral shapes, as well as those in the hexagonal system. Not sure why, but it is probably related to the symmetry.

So why do I like this malachite? Malachite is monoclinic.

Well, in this case, the malachite is replacing octahedral cuprite crystals (cuprite is in the cubic system), and more or less, retaining the cuprite shape.

But then the added bonus on this specimen, something that I didn’t spot until I was taking the photo, is a pale-coloured miersite crystal (towards the bottom right of the photo). Miersite is a rare silver copper iodide. Another addition to my Hidden Collection! And miersite is a cubic mineral. 😁

The only downside is that none of species are blue!

Below: Malachite after Cuprite, Miersite, Block 14 Open Cut, South Mine, Broken Hill, New South Wales. Width of view 6mm. Click on the image for a higher resolution version.