On 10/10/2014 1:04 PM, Kate Brodie wrote:
> black in hand specimen regardless of mineralogy
You can find black ultra-fine-grained cataclasites composed of 90%
quartz. This is probably something that can be explained with optics,
since, at grain size of a few microns, the size of individual grain
facets approach the visible light wavelength (0.4-0.7 micrometer).
Other tricky rocks are tourmaline veins that can be found sometimes
injected in fault zones.
Best,
andrea
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Andrea Bistacchi
Department of Earth and Environmental Sciences
Universita' degli Studi di Milano Bicocca
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