ˈtridəˌmīt noun
( -s )
Etymology: German tridymit, from Greek tridymos threefold (irregular from tri- three + didymos twin) + German -it -ite; from its common occurrence in trillings — more at tri- , didym-
: a mineral SiO 2 that is a silica, differs from quartz in its usually minute thin tabular orthorhombic forms of crystallization, and is found in cavities in trachyte and similar rocks (hardness 7, specific gravity 2.28-2.33)