石英

Quartz is the most abundant mineral exposed at Earth's surface — and despite its commonness, it produces some of the finest collector specimens in mineralogy. From Himalayan ice-clear crystals to the deep purple amethysts of Vera Cruz, quartz is the species every collector returns to.

Notable varieties

• Amethyst (purple, Fe-bearing)
• Citrine (yellow, heat- or radiation-induced)
• Smoky Quartz (brown to black, radiation damage)
• Rose Quartz (pink, Ti/Fe inclusions)
• Rock Crystal (colorless)
• Morion (opaque black)

The Chinese angle

Tibetan and Sichuan high-altitude pegmatites produce extraordinarily clear quartz crystals with fine terminations and minimal inclusions. The Yaogangxian district yields milky quartz matrix material for fluorite specimens, while Hunan produces noted fenster (window) quartz.

Varieties of quartz

Quartz is a parent species — the following named varieties differ in color or chemistry but share the same fundamental mineralogy.

• Smoky Quartz (烟晶)
  smoky brown to black
  Brown-to-black quartz colored by natural radiation effects on aluminum impurities.
• Milky Quartz (乳石英)
  opaque white
  Microscopically-fluid-included white quartz variety.
• Prasiolite (绿水晶)
  pale leek-green
  Heat-treated pale-green amethyst, sold as gem variety.
• Ametrine (紫黄晶)
  purple-yellow zoned
  Naturally-zoned quartz with both amethyst and citrine zones in one crystal.
• Aventurine (东陵石)
  green with mica shimmer
  Quartzite with fuchsite/hematite mica inclusions producing aventurescence.
• Tiger's Eye (虎眼石)
  golden-brown chatoyant
  Quartz pseudomorph after crocidolite asbestos with golden chatoyancy.
• Rutilated Quartz (金红石发晶)
  clear with golden needles
  Clear quartz containing golden rutile needle inclusions.
• Herkimer Diamond (赫基蒙水晶)
  water-clear doubly-terminated
  Doubly-terminated quartz crystals from Herkimer County NY, water-clear.