Howlite

Howlite is a calcium borosilicate mineral, white with gray veining, and is frequently dyed to imitate turquoise. Howlite forms in evaporite deposits - environments where mineral-rich water evaporates, concentrating dissolved minerals until they crystallize. It specifically occurs in borate-rich evaporite sequences, where boron from volcanic activity accumulates in enclosed basins.

The mineral typically forms as irregular nodules or masses with a distinctive white color and gray to black veining pattern (which is actually the matrix material the howlite grew within). Individual crystals are extremely rare - howlite almost always occurs as massive, cauliflower-like nodules.

Howlite's fame in the crystal world is paradoxically tied to its role as an impostor. Because it's porous, soft, and white, it absorbs dye readily and can be colored to imitate turquoise, lapis lazuli, red coral, and other more expensive stones. More howlite is probably sold dyed than in its natural white form.

Natural howlite is white with distinctive gray-black veining in an irregular web pattern. At hardness 3.5, it's soft enough to scratch with a copper coin. The porcelain-like luster and light weight help distinguish it from other white minerals.

The key identification scenario is recognizing DYED howlite masquerading as other stones. Blue-dyed howlite sold as 'turquoise' shows dye concentrated in the veining (the veins absorb more dye than the surrounding material) and the color rubs off on a wet cloth. Under the dye, scratching reveals white base material.