Calderite (?) (or another Garnet species) (ex Kay Robertson Collection)

Item Description

Calderite is a rare Garnet species, that for many years was actually not regarded as an actual species. It's somewhat of an intermediary species chemcially as it contains manganese, calcium, iron and aluminum. With that said, I'm not 100% certain that this piece is actually Calderite, as the color is not quite right. Calderite should be on the warmer end of the spectrum, and this piece shows a distinct dark green hue. Additionally, the label refers to the species as being a chromium and iron-bearing Garnet and states that it's ("under investigation"). The label also states that it's from Usakos, S. W. Africa (modern day Namibia), and the only locality for the species that I can find in Namibia is the type locality at Otjosondu. Sharp, lustrous, rich green colored crystals up to 5 mm can be seen all over the display side of the specimen. This is definitely a Garnet species, but as I said, I cannot say for certain if it's actually Calderite. I've seen dark green Andradite that was labeled as coming from Usakos years ago, so this very well could be Andradite. Ex Kay Robertson Collection (#6698). Kay is a prominent California collector, who specialized in European classics (see the article in the March-April, 2007 Mineralogical Record and the 50+ page article in the German Magazine "Mineralien Welt" November-December 2017).