I have faceted a number of tourmalines, so I may be able to help
with the questions.
Does any one know how to best facet a piece of black or green
tourmaline. The green tourmaline is green in one direction and
darker green in another. The darkness may be because of a fracture
in the stone.
I have never seen a facetable black quartz crystal. (Dark brown
smoky quartz, yes.)
The darkness seen along the length of a crystal (the “c” axis) is
often encountered in tourmaline, and is caused by dichroism. It may
adversely affect color, but may compensated for by correctly
orienting the stone on the dop and by careful selection of the
cutting design. The best solution is not to use a tourmaline with a
closed c axis. Black tourmaline is not affected.
Do I orientate it a certain way? Does it have cleavage planes?
Orient for best color. Tourmaline has no cleavage but may be fragile
and even self-destruct during cutting.
Also How does one polish the stone? With linde a, cerium oxide, or
a fine diamond powder such as 14,000 grit or 50,000 grit?
Tourmaline does not polish well with cerium oxide. I Use aluminum
oxide on a suitable lap (tin, Darkside, etc.) Chrome oxide produces
good results, too. 50K diamond may produce a reasonable polish,
using the correct lap. 14K works for cabochons, but is at best a
pre-polish for faceting.
Is it same for a black tourmaline. Need to make a Renaissance
style ring with a black stone. Any suggestions as to the stone to
The usual assumption is that a stone to be faceted is transparent.
This is not true of the typical black stone. It is possible to facet
an opaque or somewhat translucent stone, such as a black onyx or
black spinel, or even black tourmaline, if it is free of fractures.
The stone you select may depend on availability of the size you need
for the ring rather than the type of material.
An opaque material allows cutting the crown only, like a rose cut,
so you can use thin rough.