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不同类型的斜长石

钠长石的分数\ ce {NaAlSi_3O_8}和钙长石美元$ \ ce {CaAl_2Si_2O_8} $,我称之为\ ce {Ab}和$美元\ ce{一}$在以下列表中,出现在一个斜长石常用于定义在以下方式:

钙长石:$ \ ce{一}= 90 \ % \ % -100,美元\ ce {Ab} = 0 \ % -10 \ %;
倍长石:$ \ ce{一}= 70 \ % \ % -90,美元\ ce {Ab} = 10 \ % -30 \ %;
拉长石:$ \ ce{一}= 50 \ % -70 \ % $,$ \ ce {Ab} = 30 \ -50 \ % %;
中长石:$ \ ce{一}= 30 \ % \ % -50,美元\ ce {Ab} = 50 \ % -30 \ %;
奥长石:$ \ ce{一}= 10 \ % \ % -30,美元\ ce {Ab} = 70 \ -90 \ % %;
钠长石:$ \ ce{一}= 0 \ % \ % -10,美元\ ce {Ab} = 90 \ % -100 \ %。

什么我不知道的是这些分数是为了申请质量,物质的量浓度,体积。

回答

我想增加@SabreTooth正确答案,并添加以下:1。斜长石在本质上一般有一个钾长石组件:$ \ ce {KAlSi3O8} $。所以斜长石晶体可能是48%的钙长石,48%的钠长石和钾长石4%。这个组件通常写成$ \ ce{或}$组件(矿物正长石之后)。这引入了一个新的问题。假设你有斜长石成分$ \ ce {An49Ab46Or5} $。通常你会认为矿石是一个中长石,因为它49% $ \ ce{一}$。然而,如果你想要项目三元长石矿物到斜长石的图,你需要正常化$ \ ce {An52Ab48} $。现在这是一个闪光拉长石!所以它是哪一个? Well, there are no defined rules for determining it. However, it doesn't really matter. Remember that these names are artificially divided by us humans. Nature is not so nicely divided but rather quite continuous. Another reason is doesn't really matter is... 2. Plagioclase in igneous rocks (which is where you are most likely to find it) is rarely homogenous. It is commonly **zoned**, meaning that its composition varies across the crystal. Here are maps of $\ce{Ca^2+}$ and $\ce{Na+}$ distributions inside plagioclase crystals: ![Plagioclase X-ray maps][1] <sup>source: http://serc.carleton.edu/details/images/8598.html</sup> Brigher colours correspond to higher calcium contents. Each crystal has different composition in different zones! It may be labradorite in the cores whereas the rims would be andesine or oligoclase. Sometimes you may encounter a single crystal exhibiting the entire range from bytownite to oligoclase, which are the compositions that currently occur in igneous rocks. So the exact composition of the plagioclase is meaningless. What about albite and anorthite? These two extreme cases deserve a special treatment. 1. Albite is technically not even a plagioclase, but rather an alkali feldspar. It occurs in settings which are not your usual igneous rock: low grade metamorphic rocks, metasomatic rocks, pegmatites, etc. In this case the identity of the crystal is indeed interesting, and it is rarely called "plagioclase", but rather "albite". 2. Anorthite is extremely rare on Earth. Even the so called "anorthosites" (rocks composed almost entirely of plagioclase) contain labradorite and not true anorthite. Conversely, anorthite (as $\ce{An_{95-98}}$) is the main constituent of Lunar anorthosites. These unique rocks and minerals truly deserve to be called anorthites. [1]: http://i.stack.imgur.com/A7C03.jpg

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\ begingroup美元谢谢你的非常有趣的细节! \ endgroup美元
- - - - - -少数民族工人
2015年1月23日,十六
2

\ begingroup美元奇妙的答案!我常常想知道钾长石分解成。谢谢你这细节! \ endgroup美元
- - - - - -user889
2015年1月23日22:06

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