A fairly large specimen of tantalite.

For this week’s picture, here’s an image of a tantalite mineral specimen. I snapped this picture when I visiting a university last week — the mineral stood out for me amidst a collection of numerous rocks and minerals that were on display for geology students. I’d seen tantalite before — I’ve observed it under the microscope in heavy mineral concentrates. However, I’d never seen such a big example of it before (it’s about 2-3 cm across). This specimen may not look like much — it’s a plain dark gray mineral. However, tantalite is an important mineral since it’s a key source of tantalum, a rare and valuable metal. One more thought: this specimen looks as if it probably came out of a pegmatite. You can see that the gray tantalite crystal is still attached to another large crystal — of feldspar, I believe.