Leucite Phonolite, Vesuvius.

This is a typical example of the lava and ejecta found at the summit cone of Vesuvius. A potassium rich lava characterised by phenocrysts of leucite, dark in xpl because of low birefringence, but showing complex twinning. Clear in PPl with rounded shapes. Pyroxene shows bright colours in XPL and both growth and sector zoning. Sanidine plagioclase laths, showing some yellow colour as this slide has been left slightly thick to better show the leucite.
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