A layered "gabbroic" rock. The mafic minerals are olivine and pyroxene, the felsic mineral is plagioclase. Note:
i) the concentration of mafic minerals at the base of each unit;
ii) the decrease in grain size upwards in the complete unit shown;
iii) the very sharp top to this unit. These features are typical of cumulate rocks, i.e. those thought to have formed by the successive accumulation and crystallisation of discrete crystal - magma units in a convecting magma chamber.
Scale: overall length of opened hand lens is 80 mm
Grid reference: 965 384
This page is maintained by Roger Suthren
Last Modified: 23 October, 2008