Hi everyone!
I'm in the middle of writing up some petrological notes for my thesis, so I thought I might share some images thin sections of lepidolite bearing rocks from the Blue Jacket tin pegmatite: [
www.mindat.org]
The first shows off the bright interference colours (2nd order) of lepidolite, which some people might note is lower than muscovite. The streaky colours are a result of the common 'ball-peen' lepidolite habit.
The second shows a long, flaring lepidolite crystal. You will notice all of the quartz in the background has sutured grain boundaries. The poor old pegmatite has gone through a slight metamorphic event, and all of the quartz has been recrystallised. I left this slide a little bit thick, so the birefringence colours are a bit higher than they should be, getting towards normal muscovite colours.
The third is of a lepidolite that has been cut close to its basal cleavage, and we get a good look at how spectacular the ball peen habit can get down the microscope! You could swear that these prismatic shapes are in three dimensions, but it's just a result of oscillating growth along the a and c axes of the crystal.
I think I like these colours better than the colours you get in hand specimen!
