ALEXANDRITE
|
Alexandrite
is a variety of chrysoberyl that displays a colour change depending on light
conditions and the angle it is view from (pleochroism).The ideal colour
change would be fine emerald green to fine purplish red, but this is rare and
expensive. Alexandrite was discovered in the Ural Mountains of Russia in the
1830's, and named after tsaravitch Alexander, the future tsar. That area was
mined for over 60 years and still today Russian Alexandrite is considered the
best quality. Today, small quantities of Alexandrite are mined in
Colour:Green in daylight and red-violet in incandescent light. Hardness: 8.5 |
AMBER
|
Amber is the
fossilized resin from ancient forests. In ancient times the resin dripped and
oozed down trees, filling fissures and trapping debris such as seeds, leaves,
feathers and insects. The resin then became buried and fossilized through a
natural polymerisation creating amber. The two main sources of amber in
today's market are the Baltic states and the
Hardness: 2.5-3 |
AMETHYST
|
Amethyst is
a transparent purple quartz. Origin of name from the Greek -amethystos-
"not drunken". Amethyst was considered to be a strong antidote
against drunkenness. Greek legend tells the story of a maiden Amethystos who
was pursued a drunken god called Dionysus. She prayed to the goddess Artemis
to remain chaste. The goddess granted her prayer, transforming her into a
white stone. Filled with remorse Dionysus cried tears of wine over the stone
turning it purple.
Different localities can produce a unique amethyst to that particular region or even to that particular mine. It is mined in Colour:the colour range varies from pale lilac to deep purple. Hardness: 7 |
AQUAMARINE
|
Aquamarine
belongs to the gemstone family of Beryls. Origin of name Latin
"aqua"meaning water and "mar"sea. Legend has it that
Mermaids tails were made of aquamarine. Aquamarine is usually free of
inclusions and possesses a superior brilliance. The more intense the colour
of an Aquamarine, the higher its value.The principle supply of aquamarine
stones comes from Brazil, Russia, Afghanistan, India and Pakistan
Colour:pale blue to light greenish Hardness: 7.5-8 |
BLOODSTONE/ HELIOTROPE
|
Bloodstone
or heliotrope, is a form of Chalcedony, a cryptocrystalline quartz.
Bloodstone is green jasper with red inclusions. The red is sometimes caused
by iron oxide or red jasper. Origin of name: From the red spots looking like
spots of blood. It is usually cut "en cabochon" (that is shaped and
polished usually with a flat bottom and a convex top) or into beads, it is
used as a sealstone and in signet rings. Bloodstone is found in
Colour: green with red inclusions Hardness: 7 |
APATITE
|
Apatite is
part of the phosphate mineral group. Origin of name: From Greek apate meaning
deceit alluding to its similarity to other more valuable minerals such as
olivine, peridot and beryl. Apatite is found in different worldwide locations
like:
Colour: varies from being transparent to opaque, with colours ranging from yellow, green, blue, violet and colourless. Hardness: 5 N.B.This stone is very sensitive to heat and care needs to be taken. |
CITRINE
|
Citrine is a
form of quartz with ferric iron impurities and is rarely found naturally.
Origin of name from the French word "citron" meaning lemon. Also
called citrine quartz. Most commercial citrine is in fact heat treated
amethyst or smoky quartz.
Colour: the different shades range from yellow, gold, orange brown shades of transparent quartz. Hardness:7 N.B. Citrine and Amethyst are the exact same minerals, the only difference is the level of oxidation of the iron contained in the mineral. As this can be done artificially by heat or irradiation a large majority of Citrine sold today is heat treated amethyst. There are currently no scientific ways to determine if Citrine was changed artificially. |
CORAL
|
Precious
coral or red coral is the common name given to Corallium rubrum. The hard
skeleton of red coral branches is made up of mostly calcium carbonate and is
durable and intensely coloured. Coral can be polished to a glassy shine.
Usually deep water corals have light colour and shallow water corals have
deep colour. Coral jewellery has been found in ancient Egyptian and
prehistoric European burials and continues to be made to the present day. Due
to its softness and opacity, coral is usually cut as a cabochon or used to
make beads.
Hardness:3.5 |
CUBIC ZIRCONIA
|
Cubic
zirconia or CZ is a synthetic variant of the mineral baddeleyite which is
extremely rare in nature. It is the oxide of the metallic element zirconium,
zirconium dioxide. It was first used in the Russian space program to serve as
a window to photograph through, it was not used in jewellery until 1969 when
somebody decided to facet the material. It is often used as a diamond
simulant. Cubic zirconia should not be confused with zircon, which is a rare
naturally occurring gemstone.
Colour: By adding other minerals in the creative process CZ's can come in any colour as well as the colourless variety. Hardness:8.25-8.75 N.B. Key features that distinguish CZ from diamond: Cubic zirconias have more dispersion than diamonds so show more fire. A CZ has a Mohs rating of 8.5-9 and Diamonds have a rating of 10. A CZ is 1.7 times heavier than a diamond of equivalent size. CZs are optically flawless whereas the majority of diamonds have inclusions or flaws CZ has a refractive index of 2.176, compared to a diamond's 2.417. CZ can be made in most cases entirely colourless: equivalent to a perfect "D" on diamond's colour grading scale but it is rare to find diamonds are truly colourless. CZs are thermal insulators whilst diamonds are among the most efficient thermal conductors. |
DIAMOND
|
Diamonds are
a form of carbon. Origin of name: From Greek for invincible. Please click here to go to our more comprehensive
section on Diamonds.
Colour: it is rare to find diamonds are truly colourless. Hardness: 10.00 |
COLOURED DIAMONDS
|
Diamonds
come in all colours but these natural Fancy Colour Diamonds are rare and can
be very expensive. One out of 10,000 normal diamonds is a fancy colour diamond.
The colour of a fancy coloured diamond is measured differently to a normal
diamonds. The grading scale is based on the intensity of the colour. The GIA
fancy colour grading scale is: Faint, Very Light, Light, Fancy Light, Fancy,
Fancy Intense, Fancy Vivid, Fancy Deep and Fancy Dark.
|
EMERALD |
Emerald is a
valuable Beryl that owes its colour to chromium or vanadium, which make it
the bright green. Origin of name emerald is said to be a Sanskrit word
meaning green (Sanskrit is a classical language of
Colour: Emeralds come in many shades of green and bluish green. Hardness: 7.5-8 N.B. Many emeralds are treated to hide surface-reaching breaks and improve transparency. |
FIRE OPAL
|
Fire opal is
a bright orange variety of opal.
It is primarily found in Colour:Fire opals are transparent to translucent opals with warm body colors yellow, orange, orange-yellow or red. Hardness:5.5- 6.5 |
GARNET
|
Garnets are
nesosilicates. 0rigin of name: from ancient Greeks as colour reminded them of
the pomegranate seed or granatum. Garnets do not show cleavage (the tendency
of crystalline materials to split along definite planes, creating smooth
surfaces) so when they fracture under stress, sharp irregular pieces are
formed. Because the chemical composition of garnet varies, the atomic bonds
in some species are stronger than in others. The harder species are often
used for abrasive purposes. It is found in the regions of
Colour: virtually all colours Hardness:6-7.5 |
IOLITE
|
Iolite is a
blue silicate mineral that occurs as crystals or grains in igneous rocks,
Origin of name: from the Greek ios, which means violet. Iolite changes
colours (pleochism) depending upon which angle it is viewed from and the gems
are cut to take advantage of that. It is found in
Colour: Transparent, violet-blue, light blue, blue, rich blue-violet stone Hardness 7.5 |
IVORY
|
Ivory is a
hard, white, opaque substance that is the bulk of the teeth and tusks of
animals such as the elephant, hippopotamus, walrus, mammoth and narwhal.
Ivory had been used for thousands of years for tools, implements and weapons
and for carving and jewellery. The 1990 Convention on International Trade in Endangered
Species (CITES) put
a ban on international ivory sales to lessen the threat to endangered species
by poaching. A species of hard nut sometimes called vegetable ivory or
"tagua" is gaining popularity as a replacement for ivory.
|
JADE
|
The term
"jade"refers to two different, yet similar semi-precious
metamorphic mineral gemstones, Jadeite and Nephrite. Nephrite and jadeite are
resistance to breakage and chipping and due to their toughness they made a
superior weapons and tools for early man. Not until the 19th century that a
French mineralogist determined that "jade" was in fact two
different materials. Nephrite is usually only green and creamy white, while
jadeite can have the full range of jades colours. Jade is mined in the
regions of
Hardness:6 |
JASPER
|
Jasper is
microcrystalline quartz and is made from very small grains, it is a
semi-translucent to opaque. Jasper has been used for thousands of years as tools
and weapons during prehistoric times and for ornaments and jewellery later.
Origin of name from the Greek iaspis. Jasper is commonly found in the regions
of
Colour: dark green,yellow, brown, green, yellow, red and white. Hardness: 6.5 to 7.5 |
JET
|
Jet is a
hard gem variety of Lignite. Jet is a type of brown coal, a fossilised wood
of an ancient tree similar to our present monkey puzzle trees and cypress
trees. These trees flourished in the Jurassic period when the trees died and
fell they were eventually washed into rivers and seas to lie at the bottom
for millions of years. All the other sediment built up causing great
pressure, which flattened the wood and together with chemical changes altered
the wood to jet. Jet has been used in Jewellery since ancient times and Queen
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LAPIS LAZULI
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Lapis lazuli
is an opaque to translucent precious gemstone composed mainly of lazurite and
calcite. Origin of name from the Persian "lazhward", which was the
name of a place in modern Turkestan known for its deposits of lapis lazuli
(“stone of lazhward”). The finest colour is intense blue, lightly dusted with
small flecks of golden pyrite. Polished Lapis can be made into jewellery. In
the past it was also ground and processed to make the pigment Ultramarine for
tempera paint and oil paint.
Colour: Deep azure blue to light blue, bluish green Hardness: 5.5-6 |
LARIMAR
|
Larimar is a
semi-precious blue variety of pectolite, Sodium Calcium
Silicate Hydroxide. It was discovered in the
Colour: pale blue to sky blue Hardness: 5 |
MARCASITE
|
In
jewellery, iron pyrite used as gem is improperly termed "marcasite"
Origin of name from Arabic or Moorish for pyrite. Pyrite and Marcasite share
the same exact chemical make up; however they both differ in their interior
structure." Marcasite" is frequently found in inexpensive silver
jewellery and watches. It was fashionable and popular in Victorian and other
times where it was often used to imitate diamonds. In better quality
jewellery it is hand-set with grains or beads of metal from the setting being
pushed over the edges of the stones." Marcasite" occurs world-wide
and is easily found in the chalk near
Colour: metallic Hardness:6-6.5 |
MOISSANITE
|
Naturally
occurring Moissanite was discovered in 1905 by Dr. F.H. Moissan, a French
chemist and Nobel Prize winner and was named after him. Natural moissanite is
very rare and is limited to iron-nickel meteorites. Virtually all of the
moissanite sold in the world is synthetic. Synthetic moissanite is also known
as silicon carbide after its chemistry (in industry moissanite is known as
the man-made abrasive Carborundum). Moissanite is used as a diamond
substitute as it is transparent and hard with a slightly higher refractive
index than diamond. Moissanite jewels are cut to minimize their double
refraction or birefringent effects. It is lighter and much more resistant to
heat. This results in a stone of higher lustre, sharper facets and good
resilience. Moissanite remains undamaged by temperatures used to melt gold.
Colour:rarely clear to shades of very pale green. Hardness:9.5 |
MOONSTONE
|
Moonstone is
the best known gem variety of orthoclase feldspar. It is usually polished as
a cabochon. Its importance as a gemstone arises because of adularescence, a
floating light effect and sheen, compared to the light of the moon. This
phenomena results from alternating layers of two kinds of feldspar,which
cause light to scatter. Moonstone specimens commonly exhibit chatoyancy (a
mobile, wavering striped reflection), and sometimes display a strong cat's
eye.
Colour: most desirable colour of moonstone is blue, but it also occurs in grey, white, pink, green and brown. Hardness: 6 to 6.5 |
MYSTIC TOPAZ
|
Mystic topaz
is a treated clear topaz, it is not found naturally. To create mystic topaz,
natural, colourless topaz is coated with a thin layer of titanium. The
coating is only microns thick and is applied to the stones pavilion, the
underside angled portion that typically forms the bulk of the gem. The
specialized coating alters the stones natural refraction, creating rainbow
colours, predominantly blues, greens, yellows, and small bursts of red
shades.
N.B. this stone should be treated with care |
Onyx ia a
chalcedony that occurs in bands of different colours. Onyx refers to a black
and white banded variety of Agate and brown varieties are named Sardonyx. It
is composed of relatively straight, parallel layers of different colours.
This structure lends itself to cameo making.
It is usually cut into cabochon, or into beads, and is also used for intaglios and cameos. Some onyx is natural but much is produced by the staining of agate. It is available in the regions of Hardness: 7 |
|
Opal is a
type of quartz. Origin of name: from Sanskrit (Sanskrit is a classical Indian
language) upala = precious stone. They are luminous and iridescent with
inclusions of many colours. Opals show a play-of-colour (a shifting of
spectral colours)Opals are found in the regions of Mexico, Brazil, USA,
Japan, Honduras, Kenya, Czechoslovakia, Peru, Canada but by far Australia is
the main source of opals, almost ninety-five per cent of all fine opals come
from the dry and remote outback deserts.
Colour: White, black, red, orange, most of the full spectrum, colourless, iridescent. Very infrequently of a singular colour. Hardness: 5.5- 6.5 |
|
|
Colour: white or cream, but the colour can vary according to the natural colour of the nacre in the various species of mollusc used. Can also be black or various pastel shades. Pearls (especially freshwater pearls) can be dyed yellow, green, blue, brown, pink, purple, or black Hardness: 3.5 to 4.0 N.B.To test if a pearl is natural, rub across your across the edge of your teeth; real pearl feels rough, simulated feel smooth. |
PERIDOT |
Is the gem
quality variety of the mineral olivine. Origin of name either the Arabic word
faridat meaning "gem" or the French word peritot meaning
"unclear". Peridot is one of the few gem stones that come in only
one colour. The depth of green depends on how much iron is contained in the
crystal structure. It is found in the
Colour: varies from yellow-green to olive to brownish green. Hardness: 6.5 - 7 |
QUARTZ
|
Quartz is a
crystalline rock or mineral composed of silicon dioxide. Quartz is the second
most common mineral in the Earth's continental crust and found in all types
of geological environment. There are 49 variety's, a number of which are
gemstones, some of which are very beautiful and very rare. Origin of name
from Saxon word Querkluftertz = cross-vein ore.
Colour: colourless, white, gray, yellow to brown to black, violet, pink Hardness: 7 |
RUBY |
Ruby is the
red variety of the mineral called Corundum which is composed of aluminium
oxide (any other colour of corundrum is a sapphire, see below). The red
colour is caused mainly by chromium and titanium. It is natural for rubies to
have imperfections in them, including colour impurities and inclusions of
rutile needles known as "silk. Origin of name comes from ruber, Latin
for red. Some rubies show a 3-point or 6-point star or asterism. These rubies
are cut into cabochons to display this effect. Natural occurring rubies are
very rare and extremely rare in large sizes over 3 carats. They can be found
in many regions around the world from
Colour: pinkish red or deep, rich red colour Hardness: 9 N.B. Almost all rubies today are treated in some form (of which heat treatment is the most common practice) and rubies which are completely untreated and still of excellent quality command a large premium. Improvements used include colour alteration, improving transparency by dissolving rutile inclusions, healing of fractures (cracks) or even completely filling them. |
SAPPHIRE
|
Sapphire is
any colour of the mineral corundum other than red, those are called ruby,
(see above) corundum is composed of aluminium oxide. Sapphires tend to be
translucent or transparent and have high amounts of refraction. The most
desirable sapphires are generally those with an intense blue colour with
plenty of sparkle and life. Various shades of blue result from titanium and
iron substitutions in the aluminium oxide crystal lattice. Some sapphires
show a 3-point or 6-point star or asterism. These sapphires are cut into
cabochons to display this effect. They can be found in
Colour: Shades of blue. Hardness: 9 |
COLOURED SAPPHIRES
|
Sapphires
are mainly known for their shades of blues, but they come in an assortment of
colours.
Colour: all colours across the spectrum including white and black. Hardness: 9 N.B. It should be noted that many Sapphires can be treated to enhance or change their colour. They are heated or irradiated to produce stronger colours such as greens, yellows or even blues. While the colour of Sapphires can be changed by intense heat and radiation, it is stable for daily wear jewellery. |
SHELLS
|
Shells are
organic minerals composed of calcium carbonate . Throughout the history
shells of many types and from many different kinds of animals have been
popular as human adornments. They are often used whole and drilled so that
they can be threaded. The intricate design and varying colour patterns of
shells is mainly dependent on the diet of the animal the shell covers. Mother
of pearl or nacre is created by molluscs such as oysters and abalones
secreting a substances that consist of calcium carbonate. Nacre is
continually deposited onto the inner surface of the animal's shell creating
the iridescent nacreous layer or mother of pearl. This is done both as a
means to thicken, strengthen and smooth the inner surface of the shell.
Mother of pearl has been used as decoration from buttons to inlays in
furniture, jewellery and much more for thousands of years. Mother of Pearl
can be found in many regions including
Colour: Hardness: |
NATURAL SPINEL
|
Spinels are
composed of magnesium aluminium oxide. Most Spinel is formed due to intense
heat from volcanic activity or hydrothermal underwater streams. Origin of
name: from Latin spinella meaning little thorn, after crystal shape. Spinels
next to ruby and the rare red diamond, is the most expensive of all red gems.
With a hardness of 8 and no cleavage planes, natural spinel is a tough and
durable gemstone suitable for any kind of jewellery. Unfortunately most
Spinel that is sold commercially is synthetic.
Colour: cobalt blue, red to blue to mauve. Dark green, brown, blackgreen, pink, deep pink with an orange tinge. Hardness:8 |
TANZANITE
|
Tanzanite is
part of the zoisite mineral species and is only found in
Colour:Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet, and sage-green depending on crystal orientation. (Trichroism is the property possessed by certain minerals of exhibiting three different colours when viewed from three different directions under white lights. However, most tanzanite is subjected to artificial heat treatment to improve its colour and this significantly subdues its trichroism. Hardness: 6.5 N.B: Tanzanite is a brittle stone and although it can be worn daily, care should be taken to protect it from knocks, pressure and extreme temperature changes. Do not use a home ultrasonic to clean jewellery with tanzanite |
TOPAZ
|
Topaz is a
fluorosilicate and can contain trace elements that cause different colours
within the Topaz. Origin of name: from Greek Topazion, a
Colour: Varies in a broad range of: yellow, blue, pink, peach, gold, green, red, and brown. Hardness: 8 N.B. Topaz is often heated to change or enhance it's colour. |
TOURMALINE
|
Tourmaline
is one on the most complex gemstones of the silicate group and there are 10
different varieties created by the dozen or more elements they contain.
Origin of name: from Sinhalese turamali = stone of mixed colours. There are
Tourmalines, which change the colour from daylight to artificial light and
others display chattoyance(a mobile, wavering striped reflection).Tourmaline
is found in Africa,
Colour: depending on the variety green, red to pink, light to dark blue, colourless, purple , neon blue, brown, black, red to green and green to red. Hardness:7-7.5 N.B. Tourmaline may be heated to enhance it's colour. |
TIGERS EYE
|
Tigers Eye
is mainly composed of silicon dioxide, it is a form of quartz that acquires
fine golden lustre when polished. Origin of name: the stone resembles the eye
of a tiger. Tiger's eye is a semi precious stone with a rich yellow and
golden brown stripes that display chattoyance(a mobile, wavering striped
reflection). Tigers eye is found in regions of
|
TURQUIOSE
|
Turquoise is
composed of aluminium phosphate and copper. Origin of name: from French for
Turkish stone as in ancient days it was transported through
Colour: Blue, blue-green, green Hardness: 5-6 |
NATURAL ZIRCON
|
Zircon is
zirconium silicate, belonging
to the group of nesosilicates. Origin of name: from Arabic zarqun and Persian
zar = gold, gun = colour. Zircon is a natural forming mineral and it is not
related to the synthetic diamond substitute Cubic Zirconium which is created
in a laboratory. Zircon has a high refractive index and can be used to
imitate diamonds. It is found in
Colour: Zircon can come in red, brown, yellow, green, black or colourless. The colour of zircons below gem quality can be changed by heat treatment. Depending on the amount of heat applied, colourless, blue and golden-yellow zircons can be made. Hardness: 7.5 |
Wednesday, April 15, 2015
Popular Gemstone
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