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iamet 最新的 20 条日志
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辉石[Pyroxene] [2005-11-17]
iamet 发表在 ℃〖化学〗
Minerals composed of single chains of silicate tetrahedra sharing corners. The repeat distance between silicate
tetrahedra facing the same direction is <IMG
WIDTH="41" HEIGHT="14" ALIGN="BOTTOM" BORDER="0"
SRC="http://scienceworld.wolfram.com/chemistry/pimg28.gif"> &Aring;. In reality, the chain is twisted slightly in igneous and
metamorphic rocks. The general pyroxene formula is XYZ<font size="-1"><sub>2</sub></font>O<font size="-1"><sub>6</sub></font>, where X = Mg<font size="-1"><sup>+2</sup></font>, Fe<font size="-1"><sup>+2</sup></font>, Mn<font size="-1"><sup>+2</sup></font>,
Li<font size="-1"><sup>+</sup></font>, Ca<font size="-1"><sup>+2</sup></font>, Na<font size="-1"><sup>+</sup></font>, Y = Al<font size="-1"><sup>+3</sup></font>, Fe<font size="-1"><sup>+3</sup></font>, Cr<font size="-1"><sup>+3</sup></font>, Cr<font size="-1"><sup>+3</sup></font>, Ti<font size="-1"><sup>+4</sup></font>, Mg<font size="-1"><sup>+2</sup></font>, Fe<font size="-1"><sup>+2</sup></font>,
Mn<font size="-1"><sup>+2</sup></font> Z = Si, Al<font size="-1"><sup>+3</sup></font>, Fe<font size="-1"><sup>+3</sup></font> The most common form is (Ca,Mg,Fe)<font size="-1"><sub>2</sub></font>Si<font size="-1"><sub>2</sub></font>O<font size="-1"><sub>6</sub></font>. On the basis of
their crystal system, pyroxenes are divided into triclinic clinopyroxenes (Cpx) and orthorhombic orthopyroxenes (Opx).
There are two types of sites in each variety: M1 and M2. Because of their structure, pyroxenes can be represented with
<a href="I-Beam.html">I-beam</a> figures. A diagnostic property for differentiating amphiboles (double-chain silicates) from pyroxenes is
that amphiboles cleave at<IMG
WIDTH="27" HEIGHT="15" ALIGN="BOTTOM" BORDER="0"
SRC="http://scienceworld.wolfram.com/chemistry/pimg29.gif">, while pyroxenes cleave at 93&deg;.
<P>
<DIV ALIGN="CENTER">
<TABLE CELLPADDING=3 BORDER="1">
<TR><TD ALIGN="LEFT">Mineral</TD>
<TD ALIGN="LEFT">Formula</TD>
</TR>
<TR><TD ALIGN="LEFT">acmite</TD>
<TD ALIGN="LEFT">NaFeSi<font size="-1"><sub>2</sub></font>O<font size="-1"><sub>6</sub></font></TD>
</TR>
<TR><TD ALIGN="LEFT">aegirine-augite</TD>
<TD ALIGN="LEFT">(Na<font size="-1"><sub>2</sub></font>,Ca)(MgFe<font size="-1"><sup>+2</sup></font>Fe<font size="-1"><sup>+3</sup></font>)Si<font size="-1"><sub>2</sub></font>O<font size="-1"><sub>6</sub></font></TD>
</TR>
<TR><TD ALIGN="LEFT">diopside</TD>
<TD ALIGN="LEFT">CaMgSi<font size="-1"><sub>2</sub></font>O<font size="-1"><sub>6</sub></font></TD>
</TR>
<TR><TD ALIGN="LEFT">enstatite</TD>
<TD ALIGN="LEFT">MgSiO<font size="-1"><sub>3</sub></font></TD>
</TR>
<TR><TD ALIGN="LEFT">fassaite</TD>
<TD ALIGN="LEFT">Ca(MgAl)(AlSi)O<font size="-1"><sub>6</sub></font></TD>
</TR>
<TR><TD ALIGN="LEFT">jadeite</TD>
<TD ALIGN="LEFT">NaAlSi<font size="-1"><sub>2</sub></font>O<font size="-1"><sub>6</sub></font></TD>
</TR>
<TR><TD ALIGN="LEFT">spodumene</TD>
<TD ALIGN="LEFT">LiAlSi<font size="-1"><sub>2</sub></font>O<font size="-1"><sub>6</sub></font></TD>
</TR>
<TR><TD ALIGN="LEFT">Tschermak's pyroxene</TD>
<TD ALIGN="LEFT">CaAl(AlSi)O<font size="-1"><sub>6</sub></font></TD>
</TR>
<TR><TD ALIGN="LEFT">ureyite</TD>
<TD ALIGN="LEFT">NaCrSi<font size="-1"><sub>2</sub></font>O<font size="-1"><sub>6</sub></font></TD>
</TR>
</TABLE>
</DIV>

<P>
<a href="Polymorph.html">Polymorphs</a> of pyroxene are given in the following table.
<DIV ALIGN="CENTER">
<TABLE CELLPADDING=3 BORDER="1">
<TR><TD ALIGN="LEFT">mineral</TD>
<TD ALIGN="LEFT">group</TD>
<TD ALIGN="LEFT">symmetry</TD>
<TD ALIGN="LEFT"><a href="I-Beam.html">I-beam</a></TD>
</TR>
<TR><TD ALIGN="LEFT">augite</TD>
<TD ALIGN="LEFT">clinopyroxene</TD>
<TD ALIGN="LEFT">C2/C</TD>
<TD ALIGN="LEFT">

<IMG
WIDTH="44" HEIGHT="45" ALIGN="BOTTOM" BORDER="0"
SRC="http://scienceworld.wolfram.com/chemistry/pimg31.gif"></TD> </TR>
<TR><TD ALIGN="LEFT">enstatite</TD>
<TD ALIGN="LEFT">orthopyroxene</TD>
<TD ALIGN="LEFT">Pbca</TD>
<TD ALIGN="LEFT">

<IMG
WIDTH="44" HEIGHT="45" ALIGN="BOTTOM" BORDER="0"
SRC="http://scienceworld.wolfram.com/chemistry/pimg32.gif"></TD> </TR>
<TR><TD ALIGN="LEFT">omphacite</TD>
<TD ALIGN="LEFT">clinopyroxene</TD>
<TD ALIGN="LEFT">P2/n</TD>
<TD ALIGN="LEFT">&nbsp;</TD>
</TR>
<TR><TD ALIGN="LEFT">pigeonite</TD>
<TD ALIGN="LEFT">clinopyroxene</TD>
<TD ALIGN="LEFT">P21/C</TD>
<TD ALIGN="LEFT">

<IMG
WIDTH="44" HEIGHT="45" ALIGN="BOTTOM" BORDER="0"
SRC="http://scienceworld.wolfram.com/chemistry/pimg33.gif"></TD> </TR>
<TR><TD ALIGN="LEFT">protopyre</TD>
<TD ALIGN="LEFT">orthopyroxene</TD>
<TD ALIGN="LEFT">Pbcn</TD>
<TD ALIGN="LEFT">

<IMG
WIDTH="44" HEIGHT="45" ALIGN="BOTTOM" BORDER="0"
SRC="http://scienceworld.wolfram.com/chemistry/pimg32.gif"></TD> </TR>
<TR><TD ALIGN="LEFT">spodumene</TD>
<TD ALIGN="LEFT">clinopyroxene</TD>
<TD ALIGN="LEFT">C2</TD>
<TD ALIGN="LEFT">&nbsp;</TD>
</TR>
</TABLE>
</DIV>
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