Tincalconite is a hydrous sodium borate mineral closely related to borax, and is a secondary mineral that forms as a dehydration product of borax.

Tincalconite typically occurs as a fine grained white powder.

While most tincalconite is created by man through exposing borax to dry air, there are natural occurrences of tincalconite, as in Searles Lake, California where it was first described in 1878.

In addition to several California and Nevada locations it is reported from Argentina, Italy, Turkey and Ukraine.

The name comes from "tincal", Sanskrit for borax, and Greek, "konis", meaning powder, for its composition and typical powdery nature.