by Alan Hodgkinson
8th March 2000
A view of the Madagascan blue garnet
bought at Tucson this year.
A view of the Madagascan blue garnet
bought at Tucson this year.
It is primarily blue with secondary colour green. I have been offered various East African garnets of this kind in the past, and often purchased, but this was the first that I feel can truly be descibed as blue, though with a green modifying tint
Colour change Mauve by incandescent
light
As with the green colour change garnets from East Africa, behaviour between crossed polars is misleading. The 4 extinction and 4 illumination positions suggesting birefringence. It is, of course, strain birefringence.This is understandable when there are so many garnet species trying to squeeze into the garnet lattice.
Interesting parallel growth tubes, several quite coarse- photos to follow.
The vanadium has quite a presence,
and there is no chromium. The tiny amount of iron is borne out by
the spectrum, where the 505nm band is almost one of imagination, even by
incandescent light on white paper. To view a black surface using
a fibre optic light is deceptive, as even with no stone at all, there will
be bands about 500nm and 575nm
RI: 1.762/3
Chelsea filter: crimson
Hanneman /Hodgkinson filter:
pink
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