It crystallizes in the cubic system and is part of the pyrite group, consisting of Co2+ and Se22− ions.

[3] Hastite turned out to be the iron selenide mineral ferroselite.

Trogtalite was first found in 1955 in Trogtal quarry, Lautenthal, Harz Mountains, Germany, after which it was also named.

It has also been found in the Musonoi Cu–Co mine, Kolwezi, Katanga Province, Congo and in Argentina, in Tuminico, Sierra de Cacho, and in Los Llantenes, La Rioja Province.

It is often found together with clausthalite, ferroselite, bornhardtite, native selenium, gold, and oosterboschite.