晶礦特展

2015-04-06 05:25:38綠色花園

黑碧璽 ? (Closed C-Axis)

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這是一顆深藍發黑的藍色碧璽,從外表上看它是一顆黑色的碧璽,實際上是一顆藍色的碧璽,光軸封閉(Closed C-Axis),長軸方向兩端不透光, 垂直光軸強背光照射下可見藍色,這種光軸封閉現象,通常發生於綠碧璽和藍碧璽,原因未知,或許是因內含雜物或晶格的排列方式,導致某一方向的入射光全被吸收,有待研究.

另外一顆是鎂碧璽,強背光照射下可見棕黃色. 俺在藏家手中看過類似這樣的紅碧璽,要價太高,下不了手.

關於碧璽封閉光軸的成因和切磨方式,參考網站:

http://www.pricescope.com/forum/colored-stones/open-c-axis-t174751.html

1. Open means that lightcan travel through the c-axis and closed means that it won't. But there are all degrees of transparency, soa stone can have a 'dark', or 'slightly open' c-axis. The lighter toned stones with a dark c-axisare the tricky ones. You can find them in lighter blues pretty often, and thelow price and great color in the a-b axes make them hard to resist. But they'reoften pretty disappointing once they're cut. As for a stone with a totally closed c-axis, it will always look dead nomatter how it's cut.

2. Light cannot propagatedown a closed c-axis. Nothing can open a closed C, it is the result of theatomic conformation with the impurities or variable elements in that stone. Asthey can be wonderful in color, the thing is to find cuts that play up the aand b axes. Bar cuts are especially good for closed stones.

3. Roughly only 15% to 20%of facet-able Tourmaline crystals have an Open C Axis.

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黑碧璽? 藍碧璽?

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黑碧璽? 藍碧璽?

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黑碧璽? 藍碧璽?

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黑碧璽? 藍碧璽?

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黑碧璽? 藍碧璽?

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黑碧璽? 藍碧璽?

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黑碧璽? 藍碧璽?

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