What is "thioarsenite"

n. (context inorganic chemistry English) Any ion or derived salt in which one or more oxygen atoms of an arsenite is replaced by one of sulfur

Thioarsenite is the trianion AsS. It is a pyramidal anion, as it typical for other As(III)X compounds. It is also called sulfarsenite. It is generated by treatment of As2S3 with sulfide:

Thioarsenites are components of many sulfosalt minerals. An example is relatively common mineral proustite, AgAsS.