Dear Eric, David and Robert:
I have read the paper about the llanite (a Precambrian rhyolite with blue quartz phenocrysts), but this rock is quite different from the lithologies I am working with.
I found blue quartz mainly in metagranitoids and quartz veins, but restricted to ductile shear zones that affect these rocks. The fact that calls my attention is the close relationship between blue quartz and mylonitization. Neither microscopic observations nor electron microprobe analyses in the quartz veins, indicate presence of rutile and/or ilmenite inclusions.
Yours. Bígida
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