Fluorite

Here is a single cube of dark purple fluorite on a little bit of matrix. It displays a much lower translucency compared to some of the other specimens I've come across. A very nice example of fluorite from the ancient Lavrion mining district in Greece, an area mined for silver, lead, and other minerals most intensively from 600 BC to 100 AD and were the main source of wealth for the city of Athens during classical times. The mines were abandoned by the ancient Romans and not reopened until 1895 and then finally closed in 1984 (1).

1. More on Lavrion Mining District: https://www.mindat.org/loc-1942.html