Tachhydrite \Tach*hy"drite\, n. [Gr. tachy`s quick + "y`dwr
water. So named from its ready deliquescence.] (Min.)
A hydrous chloride of calcium and magnesium occurring in
yellowish masses which rapidly deliquesce upon exposure. It
is found in the salt mines at Stassfurt.
[1913 Webster]