Page 96 - Atlas of Sedimentary Rocks Under The Microscope

208,209 Other sedimentary rocks : Evaporites
Evap o r i t es

(continued)

Carnallite (KCI.MgCI2.61120) is one of the most soluble
of evaporite minerals and thus preparation of thin
sections containing it is difficult. 208 and 209 how a thin
section of an evaporite rock which is slightly thicker than
the usual 30 Jlm. The carnallite is showing bright inter­
fe rence colours. Crystals in the centre and in the lower
part oft he field of view show the multiple twinning which
is a characteristic of this mineral. The isotropic mineral is
halite and the sediment also contains small rectangular
cr)stals of anhydrite showing high birefringence.

208 and 209: Permian, Fison '.1 Borehole, Robin 1/ood's
Bay. near Whitby. North Yorkshire: ma�Jni/lcllfion x 19:
.
208 PPL. 209 X PL.
93