1) Crystalline 
A microcrystalline material is a crystallized substance or rock that contains small crystals visible only through microscopic examination. ...
• (a.) Crystalline on a fine, or microscopic, scale; consisting of fine crystals; as, the ground mass of certain porphyrics is microcrystalline.
(mi″kro-kris″tә-lin) made up of minute crystals.
Composed of tiny crystals that cannot be seen with an unaided eye. Microcrystalline minerals appear amorphous, since no apparent crystal shape can be detected.
Mi`cro·crys'tal·line adjective [ Micro- + crystalline .] (Crystallog.) Crystalline on a fine, or microscopic, scale; consisting of fine crystals; as, the ground mass of certain porphyrics is microcrystalline . 
Type: Term Pronunciation: mī′krō-krys′tă-lin Definitions: 1. Occurring in minute crystals.
Microcrystalline refers to a rock in which the crystals are too small to be seen without a microscope.
[adj] - containing crystals that are visible only under a microscope
said of a rock consisting of mineral grains that are distinguishable only under a microscope; cf. cryptocrystalline. 
adjective containing crystals that are visible only under a microscope