Buchan region, staurolite zone (Sample BB-1)

Andalusite-staurolite schist from Boyndie Bay. The bulk composition is marked "y" in the AFM diagram. The texture is strongly poikiloblastic. The left-hand part of the photograph consists of a very spongy andalusite poikiloblast (grey) enveloping biotite, quartz and opaque. On the right is a twinned staurolite crystal packed with tiny quartz inclusions.

Field of view is 3.5 mm across.