2. What is gemology?
Gemology or gemmology is the
science dealing with natural and
artificial gemstone materials. It is
considered a geoscience and a branch
of mineralogy. Some jewelers are
academically trained gemologists and
are qualified to identify and evaluate
gems.
3. What is gemstone?
A gemstone is the naturally
occurring crystalline form of a
mineral, which is desirable for its
beauty, valuable in its rarity and
durable enough to be enjoyed for
generations.
4. A gemstone or gem (also called a fine gem, jewel, or a
precious or semi-precious stone) is a piece of mineral
crystal, which, in cut and polished form, is used to make
jewelry or other adornments. However, certain rocks (such
as lapis lazuli) or organic materials that are not minerals
(such as amber or jet), are also used for jewelry, and are
therefore often considered being gemstones as well. Most
gemstones are hard, but some soft minerals are used in
jewelry because of their luster or other physical properties
that have aesthetic value. Rarity is another characteristic that
lends value to a gemstone. Apart from jewelry, from earliest
antiquity engraved gems and hard stone carvings, such as
cups, were major luxury art forms. A gem maker is called a
lapidary or gem cutter; a diamond worker is a diamantaire.
5. What is the Hardness of Mohs Scale?
The Mohs scale of mineral hardness is a qualitative ordinal
scale that characterizes the scratch resistance of various minerals
through the ability of a harder material to scratch a softer
material. It was created in 1812 by the German geologist and
mineralogist Friedrich Mohs and is one of several definitions of
hardness in materials science, some of which are more
quantitative.The method of comparing hardness by seeing which
minerals can visibly scratch others, however, is of great
antiquity, having been mentioned by Theophrastus in his treatise
On Stones, c. 300 BC, followed by Pliny the Elder in his
Naturalis Historia, c. 77 AD. While greatly facilitating the
identification of minerals in the field, the Mohs scale does not
show how well hard materials perform in an industrial setting.
Moh’s Scale of the precious and semi-precious gemstones
7. Requirements of Good Quality Gemstone
•Transparent
To be applicable to pass through light wholly, this makes to
the stone very beauty.
•No Cracks
The crack is to get inside the stone in tears that causes to
uncut to the stone for the reason of this cracks in it.
•No Inclusion and no Rutile
In mineralogy, an inclusion is any material that is trapped
inside a mineral during its formation. In gemology, an
inclusion is a characteristic enclosed within a gemstone, or
reaching its surface from the interior. According to Hutton's
law of inclusions, fragments included in a host rock are older
than the host rock itself.
9. •DIAMOND
Hardness: 10 Compositions: Carbons
Diamond is the hardest mineral on Earth , this combined with its
exceptional luster and brilliant fire , has made it the most highly prized of all
gems ,pure , colorless diamond is the most popular, but other varieties –
from yellow and brown to green, blue, pink, red, grey, and black – are also
found, depending on the impurities present. Because of the uniform
arrangement of their constituent carbon atoms, diamond crystals are well –
formed – usually octahedral with rounded edges and slightly convex faces
their perfect cleavage facilitates the early stages of fashioning but they can
only be polished by other diamonds,
•OCCURRENCE Diamond forms at high temperatures and pressures 80km
(50 miles) more underground most Diamond came from second sources ,
such as rivers and gravels, however , since discovery of diamond in
kimberlitic rock in south Africa (around 1870),its extraction has involved
processing vast quantities of rock, Australia is the main producer today:
other localities include Ghana Sierra Leone, Zaire, Botswana, Namibia, the
former USSR, the USA, and Brazil,
10. Diamond Clarity
Key Points
•Clarity is a measure of the number and size of the tiny imperfections
that occur in almost all diamonds.
•Many of these imperfections are microscopic, and do not affect a
diamond's beauty in any discernible way.
Much is made of a diamond's clarity, but of the Four Cs, it is the
easiest to understand, and, according to many experts, generally has
the least impact on a diamond's appearance. Clarity simply refers to
the tiny, natural imperfections that occur in all but the finest
diamonds. Gemologists refer to these imperfections by a variety of
technical names, including blemishes and inclusions, among others.
Diamonds with the least and smallest imperfections receive the
highest clarity grades. Because these imperfections tend to be
microscopic, they do not generally affect a diamond's beauty in any
discernible way.
11. Diamond Clarity
Flawless, Internally Flawless: No internal or external
imperfections. Internally Flawless: No internal
imperfections. Very rare.
Very, Very Slightly Included: Very difficult to see imperfections
under 10x magnification. An excellent quality diamond.'
VVS1, VVS2
FL, IF
12. Very Slightly Included: Imperfections are not typically visible to the
unaided eye. Less expensive than the VVS1 or VVS2 grades.'
Slightly Included: Imperfections are visible under 10x
magnification, and may be visible with the unaided eye. A good
diamond value.'
SI1, SI2
VS1, VS2
13. I1
Included: Blue Nile offers a limited selection of jewelry with diamonds of I1 grade
clarity. This grade of diamonds will have minor inclusions that may be visible to
the unaided eye.'
I2, I3
What Clarity Grade Is Right For Me?
•Select an "eye-clean" diamond - one that has no imperfections visible to the
unaided-eye through the crown. An excellent value, diamonds of this clarity
are much less expensive than flawless (FL) or internally flawless (IF)
diamonds, which are extremely rare and command higher prices.
•Frequently, imperfections in diamonds graded slightly included (SI) are not
visible to the unaided eye, making them an excellent value. If you're
considering a diamond with an SI clarity grade, call to speak to a diamond
and jewelry consultant who will review the diamond to ensure the
imperfections are not visible to the unaided eye.
14. •RUBY
Hardness: 8 Composition: Aluminium oxide
Ruby the given to red, gem-quality corundum – is
one of the best gemstones for jewellery settings.
Rubies may be any shade of red, from pinkish to
purplish or brownish red, depending on the
chromium and iron content of the stone
•OCCURRENCE Worldwide in igneous and
metamorphic rocks, or as water worm pebbles in
alluvial deposits The finest stones come from
Burma
15. •SAPPHIRE
Hardness 9 Composition Aluminium oxide
All gem quality corundum that is not red is called sapphire, yet this
name is popularly associated with the colour blue, but most
valuable is the clear, deep blue some stones called “colour”-change
sapphire “,exhibit different shades of blue in artificial and natural
light.
•OCCURRENCE Good quality sapphire is found in Burma, Sri
lank, and India, The best Indian sapphire is cornflower blue,
and found in Kashmir either in pegmatite’s or as wter worm
pebbles in alluvial deposits sapphire from Thailand, Australia,
and Nigeria is dark blue, and may appear nearly Black
Montana (USA) producers sapphire of an attractive metallic
blue Other localities include Cambodia, Brazil, Kenya, Malawi,
and Colombia,
16. •EMERALD
Hardness: 8 Composition: Beryllium Chromium Vanadium
Aluminium Silicate
Emerald derives its beautiful green colour from the presence of
chromium and vanadium Emeralds are rarely flawless, so stones
are often oiled to fill and disguise cracks, hide flaws and enhance
colour to minimize the loss of material, the step cut (or “emerald-
cut”, as it is known) is commonly used, but ancient engravings are
known, cameos, intaglios, and beads can make the best of a flawed
stone.
•OCCURRENCE found in granites, pegmatite’s, and schist as
well as alluvial deposits the finest emerald are from Colombia,
Other sources are Australia India Austria, Brazil, South Africa,
Egypt , USA, Norway, Pakistan, and Zimbabwe
17. •TOPAZ
Hardness: 8 Composition: Alluminium Flouro hydroxy ilicate
Topaz occurs in range of deferent colours deep golden yellow
topaz (sometimes called sherry topaz) and pink topaz are the
most valuable: blue and green stones are also popular. Natural
pink stones are rare most pink topaz is heat-treated yellow
material
•ZIRCON
Hardness 8 Composition Zirconium silicate
Zircon is almost famous for its colour less stones which
closely resemble diamond and have been used both
intentionally and mistakenly in their place
•OCCURRENCE Gem quality crystals are usually found as
pebbles in alluvial deposits
18. •SPINEL
Hardness: 8 Compositions: Magnesium Allumnium Oxide
SPINEL is found in a wide range of colours due to the presence of
various impurities andis transparent to almost opaque red spinel
coloured by chromium and iron is the most popular, although for
many years it was thought to be a variety of ruby
•OCCURRENCE spinel occurs in granites and metamorphic
rocks, and is often found in association with corundum Octahedral
crystals and waterworm pebbles in a wide range of of colours are
found in the gem gravels of Burma, Srilanka and Madagascar
•REMARK synthetic spinel has been manufactured since 1910it
has been used to imitate diamond, coloured to imitate stones such
as aquamarine and zircon, blue synthetic spinel, coloured by
cobalt, has been used to imitate sapphire The name may derive
from the Latin word spina, meaning little thorn, referring to the
sharp points on the crystals,
19. •BERYL
Hardness: 8 Composition: Beryllium Aluminium Silicate
Beryl derives its beautiful multi colures from the deserted of chromium and
vanadium Beryl are rarely flawless, so stones are often oiled to fill and
disguise cracks, hide flaws and enhance colour to minimize the loss of
material, the step cut (or “emerald-cut”, as it is known) is commonly used,
but ancient engravings are known, cameos, intaglios, and beads can make the
best of a flawed stone.
•OCCURRENCE found in granites, pegmatite’s, and schist as well as
alluvial deposits the finest emerald are from Colombia, Other sources
are Australia India Austria, Brazil, South Africa, Egypt , USA, Norway,
Pakistan, and Zimbabwe
There are many types of group beryl:-
•Red Beryl
•Morganite Beryl
•Goshonite Beryl
•Aquamarine Beryl
•Beryl
•Alexandrite Beryl
20. •TOURMALINE
Hardness: 7 Composition: Complex borosilicate
Members of the tourmaline family of the minerals have the same basic
crytal structure, but occur in many colours. Rubellite (from the latin
for red) is the name given to the pink or red variety with ruby- red
stones the most highly prized. Rubellite crystals are striated, with
triangular cross-section and a rounded outline they may also occur
with a fibrous habit, and and show cat’s eye when en cabochon.
There are many types of tourmaline:-
•Rubellite Tourmaline: read tourmaline
•Elbite Tourmaline: blue tourmaline
•Indicolite Tourmaline: green tourmaline
•Watermelon Tourmaline: green and red mixed tourmaline
•Bi color Tourmaline: any two colors mixed tourmaline
•Paraiba Tourmaline: light blue tourmaline is the rarest type of
tourmaline
21. •GARNET
Hardness: 7 Composition: Magnesium Aluminium Silicate
Garnet the blood red colour of pyrope is due to its iron and chromium content, it
rarely has inclusions , but when present they are rounded crystals or have
irregular out lines ,As with all garnets, pyrope has no cleavage, and fracture is
subconchoidal to uneven
•OCCURRENCE Pyrobe is found in volcanic rock and alluvial deposits,
and may along with certain other minerals, indicate the precence of
diamond bearing rocks localities include Arizona (USA), South Africa,
Argentina , Australia, Brazil, Burma , Scotland, Switzerland, and Tanzania.
•REMARK: pyrope come from Gteek pyrops meaning burning.
There are many types of Garnet group:-
•Rhodolite Garter: dark red garnet
•Specertite Garnet: orange garnet
•Pyrobe Garnet: blood red garnet
•Almandine Garnet: dark coffee garnet
•Hessonite Garnet: dark orange garnet
•Tsavorite Garnet: green garnet is the most rarest type of garnet group
22. •QUARTZ
Hardness: 7 Composition: Silicon Dioxide
Citrine is the yellow or golden variety of quartz, The yellow coloration,
due to the presence of iron, is also responsible for the name, derived
from the word “citrus” natural citrine is usually a pale yellow but rare:
There are three types of quartz:-
•Macrocrystalline Quartz
Rock Crystal
Amethyst
Aventurine
Eisenkiesel
Rose Quartz
Tiger's, Hawk's, Cat's Eye
24. •OPAL
Hardness: 6.5 Composition: Silica (SiO2·nH2O)
Opal is a hydrated amorphous form of silica (SiO2·nH2O);
its water content may range from 3 to 21% by weight, but
is usually between 6 and 10%. Because of its amorphous
character, it is classed as a mineral oid, unlike crystalline
forms of silica, which are classed as minerals. It is
deposited at a relatively low temperature and may occur in
the fissures of almost any kind of rock, being most
commonly found with limonite, sandstone, rhyolite, marl,
and basalt. Opal is the national gemstone of Australia.
