[meteorite-list] Two quartz questions-- one on topic, one off.

[Rob McCafferty]

> Good question as the waters get muddied on this
> quartz "rule" for
> meteorites.
> 
> How about Plagioclase feldspars - which are
> 'tectosilicates'
> ("molten(glassy) silicates")?
> 
> Then, the silicates: pyroxenes (e.g.,
> orthopyroxenes) can be transparent
> looking especially when thin.
>

Indeed they do. 
Take a look at this photo of polished Anorthosite
(>90% plagioclase feldspar)

Thanks to Harald Stehlik for the polishing ad sending
me the picture.

Rob McC


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