Any crystalline substance.
"The geologist carefully examined the sample to determine if it was any crystalline substance or merely amorphous glass."
transmitting light; able to be seen through with clarity
"the cold crystalline water of melted snow"
"crystal clear skies"
"could see the sand on the bottom of the limpid pool"
"lucid air"
"a pellucid brook"
"transparent crystal"
Of, relating to, or composed of crystals.
"The geologist carefully examined the crystalline structure of the quartz sample under the microscope."