Jeweller - September 2021

compound. Some maxixe-type beryl is also on the market with
colour resulting from a carbonate trace compound.
Demantoid, tsavorite and tanzanite
Another gemstone of many colours is garnet, and the standout
in the andradite branch of garnet is vibrant green demantoid.
With dispersion greater than diamond and a striking, rich green,
hue demantoid is one of the most valuable garnets.
Originally sourced from Russia, much of today’s demantoid
comes from Namibia.
Grossular garnet is found in a range of colours including yellow,
grey, colourless and green; indeed grossular gets its name
from the Latin word for gooseberry, the light green variety being
similar in colour to the fruit.
Annoushka x Fuli Gemstones
Aquamarine is another variety of beryl,
and owes its delicate blue-green palette
to ferrous iron. Loved for its icy skyblues
and cool sea greens, its name
originated from the Latin aqua marina,
meaning ‘water of the sea’”
The most sought after grossular garnet is the rich green
variety called tsavorite. Almost, but not quite emerald green,
tsavorite was discovered by geologist Campbell Bridges in
Tanzania in 1967.
He found another source in 1970, near Kenya’s Tsavo National
Park. Bridges and former Tiffany & Co. president Henry B Platt
named tsavorite after its Kenyan source.
On first viewing the gem, Platt observed, “Tsavorite is everything
a fine gemstone should be, and then some.”
Like tsavorite, tanzanite was also discovered in Tanzania
in 1967.
According to legend, a large bush fire swept the foot of Mount
Kilimanjaro, transforming the dull, greyish-brown material into
glittering blue and violet crystals, which not only caught the
eyes of Masai tribesmen but also the imagination of the world’s
most-prestigious jewellery houses.
This bushfire myth perfectly illustrates the chameleon-like
change that occurs when tanzanite crystals are heated to
approximately 400°C – the undesirable yellow and brown tints
disappear and the purple and blue tints deepen, resulting in
transparent, vividly-coloured material.
Tanzanite is a gem variety of the mineral zoisite, a calcium
aluminium silicate. Zoisite may be green, pink, grey, colourless
or brown in its untreated form.
Tanzanite’s unique formation has a million-to-one chance of
occurring outside the areas where it is known to be found,
making it significantly rarer than diamond and asserting its
reputation as a truly exotic gemstone.
Originally, tanzanite was confused with Kashmir sapphire and
even amethyst, due to its exquisite mix of velvety blue and
purple hues.
Chopard
David Morris
Chaumet
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