Wavellite occurs in hydrothermal vein deposits in low-grade metamorphic Al-rich rocks.  It forms radiating aggregates of blades with negligible to low negative relief (relative to quartz).  It is pleochroic colourless to pale yellow (A, B, C).  Wavellite is orthorhombic and has parallel extinction.  Maximum interference colours range to second order yellow, seen on the outer edge of the bundle of blades (lower left) in image D.  Sample is from an unknown location in Arkansas.  Images A and B are 2.2 mm across and C and D are 5.5 mm across. A, B, C ppl, D x-nicols.