SiO₂.nH₂O

SiO₂·nH₂O

These samples of opal are displayed in the Smithsonian Museum of Natural History. Opal is a not strictly a mineral, being a combination of minerals such as cristobalite and tridymite plus amorphous silica. It is represented by the general composition SiO₂.nH₂O. The sample at left is about 6 cm across and the opal gem is 55.9 carats. They are from Queretaro, Mexico.

这些蛋白石样本陈列在史密森尼自然历史博物馆中。蛋白石并非严格意义上的矿物，它由如方石英和三氧化二钛等矿物以及非晶质二氧化硅组成，其一般化学式为SiO₂·nH₂O。左侧样本宽约6厘米，蛋白石宝石重55.9克拉。这些样本来自墨西哥的奎特拉尔罗。

These opal samples are also from Queretaro, Mexico. The gem is 21.6 carats and the oval sample is 2-3 cm across.

这些opal样品也来自墨西哥的Queretaro。宝石重21.6克拉，椭圆形样品的尺寸为2-3厘米。

These opal gems are examples of the variety called "fire opal". The gems are 10.6 and 29.9 carats and are from Mexico. From the Smithsonian caption "Most fire opal is found in Mexico, typically in volcanic rock. Microscopic inclusions of iron oxide and the diffraction of light ignites the fire opal's flaming yellows and reds."

这些宝石是被称为‘火彩石’的种类的实例。这些宝石重10.6和29.9克拉，来自墨西哥。根据史密森尼的说明，‘火彩石’通常在墨西哥的火山岩中发现。微观的铁氧化物包含物和光的衍射使火彩石呈现出鲜艳的黄色和红色。

These are two more opal samples are also from Queretaro, Mexico. The gem is 14.5 carats and the mineral sample is about 7 cm across.

这些样品也是来自墨西哥的Queretaro。宝石的重量是14.5克拉，矿物样品的尺寸约为7厘米。

This ornamental piece is described as opal with diamond and corundum. This opal gem is 32 carats and is from Lightning Ridge, New South Wales, Australia. It is about 15 cm tall.

这件装饰品被描述为含有宝石和钻石的石英。该宝石重32克拉，产自澳大利亚新南威尔士州的Lighting Ridge。其高度约为15厘米。

This opal sample is about 15 cm across and is from Barcoo River, Queensland, Australia. Opal is the national gem of Australia, and there are numerous mining locations.

这个宝石样本宽约15厘米，采自澳大利亚昆士兰巴科河。宝石是澳大利亚的国石，有许多矿区。

Mindat's comments about opal: "Although it is still (2007) regarded as a valid mineral species for historical reasons, Opal is not a true mineral in the accepted sense of the word as it is composed of Cristobalite and/or Tridymite and amorphous silica (closely packed spheres form a diffraction grating to create Precious Opal)."

Mindat对蛋白石的评论：‘尽管由于历史原因，蛋白石仍被视作一种有效的矿物物种（2007年仍如此），但严格来说，蛋白石并非真正的矿物，因为它由石英玻璃（石英玻璃由非晶态二氧化硅组成）和/或方石英和/或石英组成（紧密排列的球体形成一种衍射光栅，从而形成珍贵蛋白石）。’

Opal is broken down into four types:

Opal-CT Cristobalite-Tridymite

Opal-CT Cristobalite-Tridymite（专名或术语）

Opal-C Cristobalite

Opal-C Cristobalite（专名或术语）

Opal-AG Amorphous - (Gem)

Opal-AG非晶态 - (宝石)

Opal-AN

Opal-AN（专名或术语）

Mindat: Opal

Mindat: 石英

opal 被分为四种类型：

Opal

SiO2.nH2O

SiO₂.nH₂O