Selenium (Se #34) is the next element on the periodic table for my APEX mineral collection.Wikipedia Selenium
Selenium Minerals - There are lots of minor Selenium minerals.
Penroseite ((Ni,Co,Cu)Se2) with 73% Selenium is my obvious APEX mineral. It can be found as inclusions in other minerals. The dark areas above are Penroseite. It is a trash can mineral where various elements can substitute into the main selenide (Se2) matrix. Pure selenides (e.g. NiSe2) are extremely rare.
- Amorphous, brick-red powder
- Black, vitreous form sold as beads
- Gray crystal form is most stable