crystalline (adj.)

formerly also cristal, and, erroneously, chrystal, Old English cristal "clear ice; clear, transparent mineral," from Old French cristal (12c., Modern French crystal), from Latin crystallus "crystal, ice," from Greek krystallos, from kryos "frost," from PIE root *kreus- "to begin to freeze, form a crust."

The spelling adopted the Latin form 15c.-17c. The mineral has been so-called since Anglo-Saxon times; it was regarded by the ancients as a sort of petrified ice. In the specific sense in chemistry, "body with a molecular structure that causes it to take the form of a regular solid enclosed by a certain number of plane surfaces," from 1620s.

Crystall is a brighte stone and clere with watry colour. Men trowe that it is of snowe or yse made harde in space of many yeres. Therfore the Grekes yave a name therto. It is gendred in Asia and in Cipres, and namely in the northe moutaynes where the sonne is mooste feruent in somer. [Bartholomew Glanville, "De proprietatibus rerum," c. 1240, translated by John of Trevisa c. 1398]

A top-20 name for girls born in the U.S. between 1978 and 1984. As a shortened form of crystal-glass it dates from 1590s. As an adjective, from late 14c. Crystal ball is from 1794.  Rock-crystal is the general name for transparent crystals of quartz. Crystal Palace was the name of the large building, made chiefly of glass and iron, for the universal exhibition of 1851 in London's Hyde Park.

Proto-Indo-European root meaning "to begin to freeze, form a crust."

It forms all or part of: crouton; crust; Crustacea; crustacean; cryo-; cryogenic; crystal; crystalline; crystallize; custard; encrust; Kristallnacht.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit krud- "make hard, thicken;" Avestan xruzdra- "hard;" Greek krystallos "ice, crystal," kryos "icy cold, frost;" Latin crusta "rind, crust, shell, bark;" Lettish kruwesis "frozen mud;" Old High German hrosa "ice, crust;" Old English hruse "earth;" Old Norse hroðr "scurf."