One of the main methods of separating natural quartz from
synthetic amethyst was by the detection of twinning planes in
natural quartz under use of the polariscope. This is no longer
considered a safe method since twinned synthetic quartz are now
being grown by hydrothermal method from twinned seed crystals.The
polariscope test is now no longer valid. Identification is more
safely based on the typical inclusions of the crystal: In natural
amethysts look for incuded crystals, goethite or needles,a
distinctive inclusion called thumprint or ‘zebra stripes’ or
’tiger stripes’due to twinning or partial healing along the
planes.Another inclusion in quartz are groups of prismatic
crystals. Another difference is in the distribution of colour in
the amethyst,the colour will be straight or angular in the
natural amethyst with very distint and separate zones of purple
and violet blue and or colourless. However colour zoning of
darker and lighter shades may be too subtle for use as positive
identification. Synthetic amethyst often contains bread crumb
like inclusions. In all synthetic amethyst look for traces of the
seed plate as well as strong colour banding that will be parallel
to the seed plate.Colour zoning will be more diffused in the
shades of purple and colourless but also it may be to subtle to
make a positive identification.
Synthetic quartz is grown by the hydrothermal method. The Russian
products will be usually free from inclusions. The Japanese
products contain liquid feathers and or two-phases inclusions.
Bread crumbs is often seen. Between crossed filters conical
twinning is often seen. Lots of the current synthetic material is
now coming from China. Hope this will help you.
hi francoise,
thankyou very much for a clear bit of info.
i have a question; if the synthetic amethyst is grown from a
twinned seed plate, does that produce an untwinned xtal? tia
best regards,
geo fox