祖母綠
Emerald is a mineral recognized among collectors for its crystal form and distribution, with known Chinese sources.
基本資料
| 化學式 | Be3Al2Si6O18 |
|---|---|
| IMA 代號 | Brl |
| 施特龍茨分類 | 9.CJ |
| 晶系 | 六方晶系 |
| 點群 | 6/mmm |
| 變種來源 | 綠柱石 |
| 模式產地 | (ancient), Egypt (Cleopatra mines) |
Emerald is the green gem variety of beryl, the most valued of the beryl family. Its colour is produced by traces of chromium and, in some deposits, vanadium. The finest emeralds show a pure, slightly bluish green of high saturation; almost all natural emeralds contain inclusions and fissures, and the trade fingerprints stones by their internal 'jardin' (garden).
Properties
Beryl is hexagonal, hard (7.5–8) and forms prismatic crystals. Emerald is brittle and frequently fractured, so most stones are routinely treated with oils or resins to improve apparent clarity — a practice that should be disclosed.
Occurrence
Classic sources are the Muzo and Chivor mines of Colombia, prized for their warm green; Zambia produces cooler, bluish stones, and Brazil, Afghanistan and Zimbabwe are also important. Other beryl varieties include aquamarine and morganite.
