Xanthoconite is a monoclinic dimorph of the mineral Proustite. It is a very rare mineral and only forms in very small crystals. Xanthoconite generally forms in the same deposits as Proustite, and may even form together with it in a single matrix. In addition to their differences in crystal symmetry, Xanthoconite usually has a more orange color than Proustite.
Xanthoconite is named after a combination of two Greek words: "xanthos", meaning yellow, and "konis", meaning powder, alluding to the yellowish color of this minerals streak.