ground
" is a breccia, consisting largely of chrysolite more or less altered
to serpentine, and accompanied by bronzite, pyrope, diopside, zircon
cyanite, mica, pyrite, magnetite, ilmenite, and some other minerals.
There are also fragments of shale and boulders of varying composition
in the blue ground.
The
origin of the diamonds in the blue ground has naturally been the source
of much speculation, but no theory meets general acceptÂance as yet.
One of the first suggestions was that of Professor Henry Carvill Lewis,
of Philadelphia, that the heat of the volcanic intrusion
