Verdelite
基本資料
| 化學式 | Na(Li,Al)3Al6(Si6O18)(BO3)3(OH)4 |
|---|---|
| 施特龍茨分類 | 9.CK |
| 晶系 | 三方晶系 |
| 點群 | 3m |
| 稀有度 | 稀有 |
| 變種來源 | 電氣石 |
Verdelite is the green gem variety of elbaite tourmaline — the most common colour in which gem tourmaline occurs. Shades run from yellowish and grass green to deep forest and blue-green, coloured by iron and traces of chromium or vanadium in the brighter stones.
Properties
Verdelite is trigonal, hard (7–7.5) and cleavage-free, with the characteristic striated prismatic habit and strong pleochroism of the group. Chromium-rich bright green material is sometimes distinguished as 'chrome tourmaline'.
Occurrence
It crystallises in granitic pegmatites and is found in Brazil, Madagascar, Mozambique, Tanzania, Afghanistan and the United States (Maine, California). Verdelite frequently shares pockets with the pink and blue elbaite varieties rubellite and indicolite, and bi-coloured and 'watermelon' crystals combine green rims with pink cores.