Crypto Micro and Macro Crystalline
Cryptocrystalline and microcrystalline are terms used to describe the surface of a rock or mineral that's made up of crystals too small to be seen with the naked eye. Cryptocrystalline is used correctly when referring to crystals that are so small it's difficult to see them even with powerful magnification. The prefix crypto comes from the Latin word for hidden or secret. Crystalline describes a naturally occurring solid that's made up of crystals. Microscrystalline refers to crystals which are microscopic hence can be seen with magnification.
Although not accurate, the two words are often used interchangeably in order to refer to crystals which cannot be seen with the naked eye.
Microcrystalline should not be confused with macrocrystalline which describes crystals that are either large enough that they can be seen quite easily or are large but tightly intergrown. An amethyst geode. is an example of macrocrystalline crystals.