| 环状硅酸盐的结构光性矿物学研究 |
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| 引用本文： | 叶大年.环状硅酸盐的结构光性矿物学研究[J].岩石矿物学杂志,1983,2(1):25-34. |
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| 作者姓名： | 叶大年 |
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| 作者单位： | 中国科学院地质研究所 |
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| 摘 要： | 自从伍斯特的著名论文发表以来,层状结构的矿物是以负光性为特征,链状结构的矿物是以正光性为特征,这是众所周知的。但是环状结构的硅酸盐矿物,究竟以
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A STUDY ON STRUCTURAL-OPTICAL MINERALOGY OF CYCLOSILICATES |
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| Abstract: | The optical sign and birefringence of a cyclosilicate mineral are not only
depended on the kinds of the ring of Si-O tetrahedrons and their orientations,
but also on the crystallochemical sites of cations. These cations in cyclosi-
licates may be classified into several types such as the large cations of "Mica-
type", the octahedron cations of "Benitoite-type", the tetrahedron cations of
"Beryl-type", the chain-type octahedron cations, the layer octahedron rations
of "Sandwich-type" and so on.
The one-dimentionality factor always co-exists with the two-dimentionality
factor in a crystal structure. On condition that the one-dimentionality factor
overpowers the two-dimentionality factor, the crystal has a positive birefringence,
conversely, on condition that the two-dimentionality factor overpowers the one-
dimentionality, the crystal has a negative birefringence.
In the cyclosilicates the structure elements of Si-O tetrahedron ring are a
two-dimentionality factor. The ca.tions of "Mica-type" and "Chain-type" are
always a factor of one-dimentionality resulting in a positive birefringence, on
the contrary, the rations of "Benitoite type" and "Sandwich type" are always a
factor of two-dimentionality resulting in a negative birefringence. The cyclo-
silicates with tetrahedrons of "Beryl-type" have a structure of three-dimentional
framework, and have very low birefringence. |
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