Crackle Quartz

The material is made by treatment. A piece of quartz is heated and then quenched in room-temperature water; the sudden temperature change induces fractures through the stone. The process is used either to create iridescent effects in the cracks or to open paths for dye. GIA notes that the quench-crackle-and-dye process is typically applied to inexpensive, widely available materials such as quartz, cubic zirconia and glass.

Basic gem tests identify the host as quartz. In a quench-crackled stone examined by GIA, the induced fractures were weblike and, unlike natural fractures, evenly spaced and of uniform depth; in dyed material the color concentrates along the fractures, which is a strong indication of treatment. The International Gem Society nevertheless lists quench crackling of quartz as undetectable, so an undyed cracked crystal cannot always be proven to be treated or untreated.

The induced fractures weaken the stone, so protect it from knocks. If the piece is dyed, GIA advises keeping it away from solvents such as alcohol or acetone, which can remove dye, and out of prolonged sunlight, which can fade it.

According to GIA, quartz has been quench-crackled and dyed for thousands of years to imitate more valuable gems such as ruby and emerald, and in the 1990s GIA saw for the first time quartz beads crackled and dyed to imitate amethyst. A 1917 trade article cited by Mindat already described quartz fractured by heating and rapid cooling in cold water, with or without dye, under names such as "Firestone".