Why was "tantrum" trending last week?
a widespread silica mineral, the fibrous variety of low-temperature cristobalite (compare opal) that occurs with opal and chalcedony near the surface of low-temperature hydrothermal deposits. Originally found in the bitumen veins at Lussat, Fr. (whence its name), it also occurs in the Czech Republic, Austria, and Hungary. For detailed physical properties, see silica mineral (table)