is a general name for a combination of Niobium and Tantalium ,more information on http://www.mindat.org/min-1514.html
is a metallic black stone with hardness of 6 and takes a good polish.
It comes from Eight Miles Park District,Fremont County,Colorado.
Size: 7.5x7.5x5 mm.
Weigth: 2.73 ct.