Xanthoconite is a

sulfosalt mineral Sulfosalt minerals are sulfide minerals with the general formula , where *A represents a metal such as copper, lead, silver, iron, and rarely mercury, zinc, vanadium *B usually represents semi-metal such as arsenic, antimony, bismuth, and ra ...

with the chemical formula Ag₃ As S₃.

References

Sulfosalt minerals Silver minerals Monoclinic minerals Minerals in space group 15 Minerals described in 1840 {{mineral-stub