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A modern 18k blue topaz Ring. An 18ct gold Blue Topaz and Diamond Cluster. An entrancing ring composed of a dazzling cushion cut, Blue Topaz mounted within a single row border of 24 brilliant cut diamonds. All mounted in 18ct White Gold. Topaz 13.5
x 13.5 mm
The Gem
stone Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. It is the birthstone of the month November. It crystallizes in the orthorhombic group and its crystals are mostly prismatic
terminated by
pyramidal and other
faces, the basal pinacoid often being present. It has an easy and perfect basal cleavage, meaning that gemstones or other fine specimens have to be handled with care to avoid developing cleavage flaws. The
fracture is
conchoidal to uneven. Topaz
has
a hardness of 8, a specific gravity of 3.4-3.6, and a vitreous luster. Pure topaz is transparent but is usually tinted by impurities; typical topaz is wine or straw-yellow. They may be made white,
gray, green,
blue, pink or reddish-yellow and
transparent or translucent.
When heated, yellow topaz often becomes reddish-pink. The colour change upon heating was first discovered by a Parisian jeweler around 1750. In particular the
yellow topaz
of Brazil has been treated
frequently
by
wrapping topaz in asbestos. Only stones of a brown-yellow colour yield the pink; the pale yellow ones usually turn white. The pink colour is stable. Topaz can also be irradiated, turning
the stone blue,
ranging from a light pure
colour to very
dark
almost electric blue. A recent trend in jewelry is the manufacture of topaz specimens that display iridescent colours, by applying a thin layer of titanium oxide via physical
vapor deposition,
this stone is then sold as
'mystic topaz'.
Topaz
is commonly associated with silicic igneous rocks of the granite and rhyolite type. It typically crystallizes in granitic pegmatites or in vapor cavities in rhyolite
lava flows like those
at Topaz Mountain in western
Utah. It may be found
with
fluorite and cassiterite. It can be found in the Ural and Ilmen mountains, Afghanistan, Sri Lanka, Czech Republic, Germany, Norway, Pakistan, Italy, Sweden,
Japan, Brazil, Mexico,
Flinders Island and the United
States. Some clear topaz
crystals
from
Brazilian pegmatites can reach boulder size and weigh hundreds of pounds. Crystals of this size may be seen in museum collections. The famous
Braganza diamond is in most
likelihood a topaz. The Topaz of
Aurungzebe, observed by Jean
Baptiste
Tavernier
measured 157.75 carats.
The name "topaz" is derived from the Greek Τοπάζιος
(Τοp ziοs), which was the
ancient name of St. John's Island in
the Red Sea which was
difficult to find
and from
which a yellow stone (now believed to be chrysolite: yellowish olivine) was mined in ancient times; topaz itself
(rather than topazios) wasn't really known
about before the classical era. In the
Middle Ages the name
topaz was used to refer to any yellow gemstone, but now the name is only properly applied to the silicate described above. Yellow topaz is
the traditional November birthstone, and the
state gemstone for the US State of Utah.
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FRA621BT
An18k Topaz Cocktail Ring. An unusal 18ct gold Blue Topaz and Diamond Cluster Ring.Cushion cut blue topaz. white gold
price: £2,600.00 |
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