名稱   黄玉	Name   Topaz
化學公式   Al2SiO4(F,OH)2	Chemical Formula   Al2SiO4(F,OH)2
莫氏硬度   8	Mohs scale of Hardness   8
描述   黃玉是鋁和氟的矽酸鹽礦物，通常無色，但可以是白色，黃色，淺灰色，藍色，橙色，棕色，綠色或粉紅色。與其他寶石不同的是，晶體中的雜質並不總是使黃玉具有顏色。它被用作珠寶和其他裝飾品中的寶石。黃玉晶體中有兩個主要的有色中心，它們是由晶體結構中的間隙或多餘的電子產生的。這些異常會吸收照射到晶體中的某些部分的光，從而產生黃色或藍色陰影。綠色黃玉混合了黃色和藍色中心。當鉻代替黃玉的晶體結構中的鋁時，晶體看起來是粉紅色或紅色。具有鉻雜質和黃色中心的晶體將是橙色的黃玉。	Description   Topaz is a silicate mineral of aluminium and fluorine, usually colourless, but can be white, yellow, light shades of grey, blue, orange, brown, green or pink. Unlike other gem stones, it is not always the impurities in the crystal that give topaz its colour.  It is used as a gemstone in jewellery and other adornments. There are two dominant coloured centres in topaz crystals, produced by either a gap or an extra electron in the crystal structure. These anomalies can absorb certain parts of the light shining into the crystal, to produce either yellow or blue shades of colour. Green topaz has a mixture of yellow-and blue-type centres. When chromium replaces aluminium in the crystal structure of topaz, the crystal appears to be pink or red. A crystal with a chromium impurity and a yellow coloured centre would be an orange topaz.
小挑戰   黃玉最常在哪裡找到？ 黃玉通常與花崗岩和流紋岩類型的矽質火成岩有關。它通常在花崗岩偉晶岩或流紋岩熔岩流（包括猶他州西部的黃玉山和南美的奇維納爾）的蒸氣腔中結晶。	Challenge   Where is Topaz most commonly found? Topaz is commonly associated with silicic igneous rocks of the granite and rhyolite type. It typically crystallizes in granitic pegmatites or in vapor cavities in rhyolite lava flows including those at Topaz Mountain in western Utah and Chivinar in South America.

 Reference

https://www.gemsociety.org/article/select-gems-ordered-mohs-hardness/

by Trinity Wong on 17 Mar 2021