長石
Feldspar is the most abundant mineral group in the Earth's crust — a family of aluminosilicates of potassium, sodium and calcium. It spans the potassium feldspars (orthoclase, microcline) and the plagioclase series (albite through anorthite), and is a primary building block of granite and many other rocks. Collectors prize varieties such as amazonite (green microcline), moonstone and labradorite.
基本資料
| IMA 代號 | Fsp |
|---|---|
| 晶系 | 單斜晶系 |
| 點群 | 2/m |
| 稀有度 | 常見 |
| 收藏級別 | 適合陳列 |
| 模式產地 | (general term), Worldwide |
Feldspar — the crust's default mineral
Feldspars make up more of Earth's continental crust than any other mineral family. The group splits into two branches: the alkali feldspars — orthoclase and microcline, including the turquoise-green variety amazonite — and the plagioclase series running from sodium-rich albite to calcium-rich anorthite.
The collector varieties
Collectors mostly meet feldspar through its show-off varieties: amazonite's saturated blue-green, moonstone's billowy adularescence, and labradorite's electric flash of blue-gold iridescence (labradorescence) caused by light interference within microscopic exsolution layers.
Identification notes
Two cleavage directions at roughly right angles and hardness 6 are the quick field tests; plagioclase often adds fine parallel striations on cleavage faces that alkali feldspars lack.
