Gemology

What is Gemology

Gemology or gemmology is the science, art and profession of identifying and evaluating gemstones. It is considered a geoscience and a branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems.

What Are Natural Gemstones?

Natural gemstones are delivered to us courtesy of nature, with no interference from humans. By the time they appear in our jewelry they've been cut or polished, but they've not been altered in other ways.

What Are Genuine Gemstones?

A genuine gemstones is the real thing, but isn't natural anymore if it was treated in some way to enhance its appearance.

Enhancements allow jewelry manufacturers to improve the look of gemstones that consumers wouldn't otherwise purchase. Treated gemstones are genuine, but they are no longer considered natural. If naturally "perfect" stones were the only ones available, most of us could n't afford them.

What Are Synthetic Gemstones?

A synthetic gemstone shares a natural stone's physical, chemical and optical qualities, but it is created in a laboratory. It's kind of like making a high tech batch of cookies -- we know the ingredients and we know how long to cook them. There are synthetic versions of nearly all popular gemstones and many versions have been available for a long time. Older synthetics were fairly simple for gemologists to detect, because they were often too perfect. Some modern synthetic gemstones look more natural and are more difficult to identify, but an experienced jeweler or gemologist can usually classify them.

Jewelry that includes quality synthetic gems can be just as beautiful as jewelry made with natural stones. Good synthetics aren't always inexpensive, but should cost much less than natural stones of similar quality.

Since synthetic gemstones have the same composition as their natural counterparts, they could technically be called genuine, but that would be considered deceptive labeling if the stone's origins are not disclosed. Question the ethics of anyone who knowingly omits origin information, and the expertise of anyone who cannot provide it.

Birthstone - Gemstone mapping

By Month:

March - Aquamarine , Bloodstone

December - Blue Topaz,Turquoise, Tanzonite

February - Amethyst

July - Ruby

By Day:

Monday - Pearl

Saturday - Sapphire

Friday - Topaz

Wednesday - Amethyst

Many people decide to go with jewelry that combines several birth stones into one item, a birthstone bracelet, for example. Others prefer single stones. The birthstone chart, below, will take you to either an article or a merchant site where you can get more information on that particular birth stone.

Birth Month	Modern Birthstones	Traditional Birthstones	Mystical Birthstones	Ayurvedic Birthstones	Other Birthstones
january birthstone	Garnet	Garnet	Emerald	Garnet	Rose Quartz
february birthstone	Amethyst	Amethyst	Bloodstone	Amethyst	Onyx,Moonstone
march birthstone	Aquamarine	Bloodstone	Jade	Bloodstone	Rock Crystal
april birthstone	Diamond	Diamonds	Opal	Diamond	Quartz, White Sapphire
may birthstone	Emerald	Emerald	Sapphire	Agate	Chrysoprase, Beryl
june birthstone	PearlMoonstone	Alexandrite	Moonstone	Pearl	Opal
july birthstone	Ruby	Ruby	Ruby	Ruby	Carnelian
august birthstone	Peridot	Sardonyx	Diamond	Sapphire	Jade
september birthstone	Sapphire	Sapphire	Agate	Moonstone	Lapis Lazuli, Diamond, Chrsolite
october birthstone	Opal, Tourmaline	Tourmaline	Jasper	Opal	Pink Tourmaline, Zircon, Aquamarine
november birthstone	Yellow Topaz, Citrine	Citrine	Pearl	Topaz	Diamond
december birthstone	Blue Topaz,Turquoise	Zircon, Turquoise,Lapis Lazuli	Black Onyx	Ruby

Day Of Birth Gemstones:

If you were born on:	Your Day-Of-Birth Gemstone Is:
Sunday	Topaz
Monday	Pearl
Tuesday	Garnet
Wednesday	Amethyst or Cat's Eye
Thursday	Emerald (Similar color gem in semi-precious is Peridot)
Friday	Topaz (See Blue Topaz, Smoky Topaz)
Saturday	Sapphire (Similar color semi-precious: Iolite)

Diamond Simulants

The high price of gem-grade diamonds has created a large demand for materials with similargemological characteristics, known as diamond simulants or imitations. Simulants are distinct from synthetic diamond, which unlike simulants is actual diamond, and therefore has the same material properties as natural diamond. Enhanced diamonds are also excluded from this definition. A diamond simulant may be artificial, natural, or in some cases a combination thereof. While their material properties depart markedly from those of diamond, simulants have certain desired characteristics—such as dispersion and hardness—which lend themselves to imitation. Trained gemologists with appropriate equipment are able to distinguish natural and synthetic diamonds from all diamond simulants, primarily by visual inspection.

Diamond Simulants => moissanite, cubic zirconia(CZ), rhinestones(high-leaded glass)

moissanite is almost 10% of Diamond price(Diamond Hardness = 10, Moissanite hardness = 9.5)

Moissanite is also brighter, more lusterous, and has more fire than diamond.These criteria define how "pretty" the jewel is - the shine, the sparkle, and the prismatic qualities.It is artficially made not natural.

Cubic zirconia (or CZ) is the cubic crystalline form of zirconium dioxide (ZrO₂). The synthesized material is hard, optically flawless and usually colorless, but may be made in a variety of different colors. It should not be confused with zircon, which is a zirconiumsilicate (ZrSiO₄).

Mohs scale of Mineral Hardness

The Mohs scale of mineral hardness 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 mineralogist Friedrich Mohs and is one of several definitions of hardness inmaterials science. The method of comparing hardness by seeing which minerals can scratch others, however, is of great antiquity, having first been mentioned by Theophrastus in his treatise On Stones in ca 300 BC, followed by Pliny the Elder in his Naturalis Historia circa A.D. 77.

Mohs Scale of hardness is a RELATIVE scale, not proportional. I mean by this that a mineral with the hardness of 8 will NOT be twice as hard a a 4. (For example, diamond is 40X harder than sapphire!).It is really a scale of relative "scratchability".

#1 is softest..................#10 is hardest

#1	Talc
#2	Gypsum
#3	Calcite
#4	Flourite
#5	Apatite
#6	Feldspar
#7	Quartz
#8	Topaz
#9	Corundum
#10	Diamond

Gemstones and Mohs Scale

Diamond:....................10

Syth. Moissanite:........9.5

Corundum:..................9

Cubic Zirconia:............8.5

Spinel:........................8

Topaz:........................8

Emerald:.....................7.5 - 8

Almandite:...................7.5

Rhodolite:....................7 - 7.5

Pyrope:.......................7 - 7.5

Spessartite:.................7 - 7.5

Tourmaline:..................7 - 7.5

Iolite:...........................7 - 7.5

Quartz Group: .............7

Peridot:.......................6.5 - 7

Jadeite:.......................6.5 - 7

Andradite:....................6.5 - 7

Scapolite:....................6.5

Zircon (low):.................6.5

Tanzanite:...................6.5 - 7

Feldspars:...................6 - 7

Nephrite:.....................6 - 6.5

Opal:..........................5.5

Lazulite:.....................5 - 6

Lapiz Lazuli:...............5- 6

Turquoise:..................5 - 6

Stainless Steel...........5.5

Sphene:.....................5 - 5.5

Apatite:......................5

Rhodochrosite:...........4

Coral:........................3 - 4

Refractive Index

Refractive index, or RI as it is often abbreviated, is one of the most important signatures of a gemstone. Measuring refractive index is one of the first steps in identifying a gemstone, though some gemstones have similar refractive indices and additional tests are required for a definitive identification.

RI is the ratio of the velocity of light in air to the velocity of light through a transparent material. If light passes from air into a transparent material at an angle of incidence other than a 90 degree angle, it is deflected at a different angle (the coincident angle) according to the RI. Gemstones with higher RI are generally more brilliant than those with low RI, because more light is returned back out the top or crown of the stone, instead of passing through the bottom or pavilion. Diamond has an RI of about 2.4; quartz, about 1.54-1.55. The RI of most gemstones is easily measured using a simple optical instrument known as a refractometer.

Some gemstones are singly refractive: they have only one refractive index. Other gemstones -- in fact, most -- are doubly refractive: they have two different refractive indices. When a beam of light enters a doubly refractive gem, it is split into two beams, each travelling at a different speed and on a different path through the crystal. Birefringence is a measurement of the difference between the two refractive indices in gems that are doubly refractive, and it ranges from a low of .003 to a high of .287. Very few gemstones are singly refractive; in fact, the only well-known gems with that property are diamond, spinel and garnet.

The following chart lists the refractive indices for 126 varieties of gemstones, sorted in descending order.

Refractive Index of Metals

Platinum: 2.330

Titanium: 2.160

Copper: 1.100

Nickel: 1.080

Gold: 0.470

Silver: 0.180

Gems Classfication

Gemstones in the Elements class:

• DIAMOND
• MOISSANITE

Gemstones in the Oxides class:

• CORUNDUM

Variety: RUBY
Variety: SAPPHIRE

• CHRYSOBERYL

Variety: ALEXANDRITE
Variety: YELLOW-GREEN CHRYSOBERYL
Variety: CAT'S EYE CHRYSOBERYL

• PERICLASE
• SPINEL
• TAAFFEITE

Gemstones in the Carbonate class:

• AZURITE (often in combination with malachite)
• MALACHITE
• RHODOCHROSITE (both massive and crystalline)
• SINHALITE (a borate mineral)

Gemstones in the Phosphate class:

• APATITE
• BRAZILIANITE
• TURQUOISE

Gemstones in the Silicate class:

• ANDALUSITE
• AXINITE
• BENITOITE
• BERYL

Variety: AQUAMARINE
Variety: EMERALD
Variety: GOSHENITE
Variety: HELIODOR
Variety: MORGANITE
Variety: RED BERYL

• CORDIERITE

Variety: IOLITE

• DIOPSIDE
• EUCLASE
• THE GARNETS:
• ALMANDINE
• ANDRADITE

Variety: DEMANTOID

• GROSSULAR

Variety: HESSONITE
Variety: TSAVORITE

• PYROPE
• SPESSARTINE
• UVAROVITE
• JADE (a variety of two minerals: Jadeite and Nephrite)
• KORNERUPINE
• OLIVINE

Variety: PERIDOT

• QUARTZ

Variety: AMETHYST (violet)
Variety: CITRINE (yellow to orange)
Variety: PRASIOLITE (green)
Variety: ROCK CRYSTAL (colorless)
Variety: ROSE QUARTZ (pink)
Variety: SMOKY QUARTZ (gray to black)

• PECTOLITE

Variety: LARIMAR

• SCAPOLITE
• SPODUMENE

Variety: KUNZITE
Variety: HIDDENITE

• TITANITE (also known as sphene)
• TOPAZ
• THE TOURMALINES:
• ELBAITE

Variety: INDICOLITE

• ZIRCON
• ZOISITE

Variety: TANZANITE

Gemstones in the Mineraloids class:

• AMBER
• OPAL
• TEKTITES

Variety: MOLDAVITE

Precious Metals (in the Elements class):

• GOLD
• PLATINUM
• SILVER

Planets and their Gem Stones

In Astrological works, the nine planets have been assigned nine different gemstones. According to the classical famous astrological work 'Jatak Parijat' we can divide the planets and their stones as follows:

Planet	Gem Stone
Sun (Surya)	Ruby (Manik)..
Moon (Chandra)	White Pearl (Moti)..
Mars (Mangal)	Red Coral (Moonga)..
Mercury (Budha)	Emerald (Panna)..
Jupiter (Guru)	Yellow Sapphire (Pukhraj)..
Venus (Shukra)	Diamond (Heera)..
Saturn (Shani)	Blue Sapphire (Neelam)..
Rahu	Gomedha..
Ketu	Cat's Eye (Lahusunia)..

Telugu to English translation of Gem Stones

Kempu(Maanikyam) - Ruby

Pacha(Marakatham) - Emerald

Pushyaragam - Yellow Sapphire

Gomedhikam – (Yellow)Zircon

Neelam(Indraneelam) - Blue Sapphire

Vajram - Diamond

Vaiduryam – cymophane/chrysoberyl (Cat's eye)

Muthyam - Pearl

Pagadam – Red Coral

ref:

http://en.wikipedia.org/wiki/Gemology

http://jewelry.about.com/cs/thegems/a/gem_terminology.htm

http://www.gems4friends.com/birthstones.html

http://www.gemstone.org/gem-by-gem/gem-by-gem-by-color.html

http://www.annemeplon.com/birthstones.htm

http://beautifulsilverjewelry.com/birthstonelist.htm

http://www.acstones.com/Birthstone.html

http://gilletts.com.au/information.php?info_id=39

http://gilletts.com.au/information.php?info_id=13

http://gilletts.com.au/information.php?info_id=26

http://en.wikipedia.org/wiki/Diamond_simulant

http://www.gemologyonline.com/mohs.html

http://www.galleries.com/minerals/

http://kamalkapoor.com/gemstones/gems_planet.asp