Cryptocrystalline \Cryp`to*crys"tal*line\ (-kr?s"tal-l?n), a.
[Gr. krypto`s hidden + E. crystalline.] (Geol.)
Indistinctly crystalline; -- applied to rocks and minerals,
whose state of aggregation is so fine that no distinct
particles are visible, even under the microscope.
[1913 Webster]