4 Fashionable Gemstone terms you should know in 2016

With each passing year, there is a significant rise in demand for different types of natural gemstones. In 2016, the technology of cutting and polishing gemstones has reached a “never seen before” stage where new definitions and concepts are ruling the roost. 

If you are new to gemstone industry, and are exploring the world of assembling top grade gems, here are 4 terms you should know in 2016!

1. Opal doublets 

Also called the composite opals, opal doublets are actually two gemstones glued back-to-back using resins and glues. There could be an opal as one layer glued to other materials. Man-made doublets include a well-rounded off opal glued to black industrial glass or vitrolite.

The doublets are classified as primary opal gemstone or a secondary opal, depending on the thickness of the natural gemstone. Used in jewellery, opal doublets are very hard to distinguish from their natural counterparts. 

Opal doublet is given a cabochon cut for superior gem-like finish.

2. Opal triplets

Triplets are not as extensive as doublets. The triplet has three layers-

Black base 

Thin layer of natural opal (usually white opal)

Clear slice of quartz, glass acting as a capping

The difference in layering adds weight to the opal, without compromising on the clarity and translucency of the natural gemstone.

Compared to the doublets, opal triplets are cheaper but serve just the same purpose in jewellery making, especially considering the fact that natural opal gemstone is very fragile, and often chips away.

Note:

The doublets and triplets remain intact for years, if not decades, and hence give the opal a sense of durability for a longish use.

3. B Jade

Jade is a popular ornamental rock, and counted as a semi-precious gemstone. There are two distinct varieties of jade with similar silicate crystalline structure:

Nephrite

Jadeite

“B Jade” is an artificially treated jadeite that is bleached in acid and later doped with polymer resin to enhance its look. The B Jade family has a clear, spider-web like crystalline structure bearing a smooth apple green shade. The bleaching and subsequent impregnation process leaves absolutely no trace of spotting on the surface. 

In jade gemstone market, there are different categories:

A Jade: Bee-waxed jade with no artificial treatment or bleaching 

C Jade: Dyed B-Jade 

D Jade: Dyed Jadeite 

In 2016, the B Jade is back in popularity after revisions in technology and acceptance of polymeric doping as a regularised process in lapidary.

4. Lead-glass filling Rubies/ sapphires 

Also called composite ruby gemstone and sapphire gemstone, these are hybrid gemstones made using combination of lead-glass and corundum. Natural ruby is brown and hard, which makes them hard to cut. When combined with lead-glass, the ruby transforms into a clearer and brilliant gemstone that is easier to cut. In normal market, hybrid rubies can be as much as 35%! 

Though rated as one of the least accepted heat treatment process for ruby enhancement, lead glass filling clears up the impurities and the rutile silk structure is very much conspicuous. 

The world of Assembled Gemstones is Growing Big

With the demand for natural gemstones putting immense pressure on the market, there have been resurgent rise of composite gemstones too. Called by many names in the industry, assembled gemstones or hybrids are not 100% natural material. They contain significant amount of man-made materials like glass, corundum, resin polymers and dyeing agents, but still command a position to reckon with. At least in the fashion and imitation jewellery industry assembled rubies, sapphires, emeralds and turquoise have a huge demand.

Let us dig a little about the hybrid or assembled rubies, sapphires gemstone and emerald beads.

Assemble gemstones: The definition 

An assembled gemstone is a combination of two or more materials. They could be singly natural or a blend of artificial and natural stones. For instance ruby and lead glass in Lead-glass filling gemstones. The commonly identified gemstones in the assembled categories are:

Doublets and triplets 

Inlays 

Mabe pearls 

Reconstructed, re-crystallized and restructured gemstones 

But is assembling really an alternative! Here are five popular reasons given by the manufacturers to give synthetic process a legitimate backing in the market.

Give the gemstone a greater durability making them more wearable as a daily use accessory

Boost the pricing and quality in terms of clarity, carat weight and fault filling 

Add desirable fillers and dyeing agents to make them more saleable 

Build a distinct family of gemstones that are hybrid, and not synthetic

Popular assemble gemstones

Doublets and triplet Opals

Without doubt, the doublets and triplets are popular as widely accepted hybrid gemstones. They are done exclusively for opals. White opal is used as a sandwich in triple layers, where the base is a black backing glass material, while the top surface is a translucent plastic that delivers a higher refractive index. 

Like a cementing, opal gemstones assembled as a doublet and triplets have the desired thickness and strength, without compromising on the lustre, refractive index, translucency and hardness.

 

Apart from the fragile gemstone like opal, lapis lazuli, black onyx, turquoise and quartz are other naturally extracted items cut into doublets and triplets for a fashionable market.

Mabe Pearls

Cultured pearls are susceptible to scratches and breaking. Mabe pearls are assembled gemstones using a blister dome cut apart from the mother shell. Mabe pearls can be attached back-to-back as if they look like a single wholesome pearl. 

Composite Hybrid rubies

Rubies and sapphires often carry a fault that requires filling. Fillers like dyeing agents, polymer resins and lead glass are used in the faulty gemstones. Use of composite materials as a filler occurs as an indistinct process where it is hard to detect the presence of unnatural material using unaided vision.

Point of caution:

Assembled gemstones can’t be cleaned and maintained like regular natural stones. Techniques like ultra-sound cleaning and laser treatment can affect the bond, giving rise to visible fault lines.

As a buyer, you must look for hints in the gemstone surface to distinguish the assembled gemstones from the real ones. From weight in carats to their clarity, there are many ways assembled gemstones catch the attention of usual buyers. 

 

Getting the Carat weight of gems correct

If you are in the gemstone market, apart from the obvious colour and size, there is one more very important thing that you should evaluate. And nobody is going to cheat you on this if you know how to calculate the size of a gemstone. We all it- The Carat. When it comes to finding the right sized gemstone within a budget you can handle, carats is something you should get familiar with.

What is a carat?

Gemstones are weighed in carats. Every gemologist would count the carat as the basic factor to classify different gemstones. The raw pieces are cut into smaller and smoother edges. The finished gemstones are tagged with the carat after cutting to measure up the amount of wastage in the processing. 

Abbreviated to “ct” in a gemstone parlance, a carat is a unit of measurement usually represented in points. A point of a gemstone size is 0.01 of a carat or in general terms, one unit is 1% of what we know as a carat. For very small garnets, rubies and travertine, the usual unit of size determination is a “point” and not carats. 

Carat and pricing 

The word “carat” has same origin as that of the word “keratin”. Keratin is derived from the Latin word “keratos”, meaning “little horn”. The carob tree seeds are called keratin too, and the gemstones resemble them in more than one way that you can think of. Carats signify the uniformity of different sized gemstones. 

As far as pricing is concerned, a gemstone with higher carat value is quoted at a higher price. 

A correlation: Grams versus carat

 

Until the end of World War I, gemstones were still measured in grams and not carats. After 1920, the popularity of carats caught up owing to bigger sized diamonds being cut into cabochons and smaller shapes. As a method of approximation, gem scientists and lapidary artists zeroed on to carat as an international standard. 

One carat = 1/5th of a gram

In general term, one carat is 20 percent of what we know as gram weight.

Law of gemstone pricing

Price per carat is the universal factor to identify what the gemstone might be weighing. The pricing is fixed as per a very popular hand-rule called “Indian Law” or “Tavernier’s Law”.

In a bid to find the weight of the gemstone in terms of carats, the formula used is:

Carat = Facet style factor (ff) x {Girdle length (grl) x Girdle width (grw)} x depth (dep) x Average specific weight

These days, a specially designed digital scale is used to weigh precious gemstones. The same scale can derive the combined carat weight of more than one gemstone. 

To convert a gemstone’s weight in milligrams into carat, divide it with a factor of 200.

For example, if a diamond weighs 250 milligrams, the weight in carat is: 250/200= 1.25 ct

In terms of points, this carat value is equal to 125 points.

Apart from carat of course, there are three C’s you need to define to arrive at the right price- Cut, Clarity and Colour.

Fascinating Amber: Tips to buy Natural Gemstone Variety

Amber gemstones may not feature in the list of most sought after items but they remain popular among gem collectors. Derived from resins, amber is actually a polymeric substance with little or no mineral crystal within it. Despite wide-spread availability, there is one amber family that is considered mystical and superlative in its existence. It is the group of Baltic ambers.

Here are some enticing facts about Natural Baltic amber gemstones.

Composition 

Amber is anyways a natural fossilised tree resin. Despite its heterogeneous composition, natural amber gemstone shows a distinct colour and composition consisting of plant cellulose, saps and polymeric acids. Chemically, they resemble terpene family. 

What is a Baltic Amber?

Also called Succinate, Baltic Amber gems contain 8% of succinic acid. The origin of most of these gemstones lies in Miocene era, nearly 44 million years ago. Largely comprising fossilized plant resin, Baltic Amber also contains animal and insect inclusions giving them a rather colourful hue, distinct from other amber gems. Dominican Amber is one of the sub-species of Baltic Amber. 

How to identify true amber?

Intensity of colour and transparency are clear cut factors that represent the purity of natural amber. The accepted colour range varies between clear citric limes to golden brown cognac. Expensive amber varieties resemble egg yolk yellow with minute red rutile. There are translucent and opaque varieties of amber too that contain higher quantity of acids. 

There are 5 coloured amber gemstones sourced to the market.

Yellow amber (contain nearly 70% plant resins)

Red Amber (Also called Cherry Amber, it forms only 2-3% of the total availability)

Green Amber (known as Caribbean amber, it is also a very rare variety and is probably the costliest in the lot)

Blue Amber (Dominican Blue Amber is rarest in the family and has percentage of petroleum hydrocarbons) 

Black Amber (Often extracted alongside Ammolite and Korite)

Heat treatment on Amber 

The colour and consistency of appearance of amber is improved by subjecting them to heat treatment and subsequent dyeing. The agents used are natural plant oils and solvents like canola oil. It often results in circular cracks, known as sun spangles.

How to identify pure amber

Unlike a mineral stone, amber is warm. Its density is lower than sea water, so it will float on the surface. The purest amber gemstone is called ‘antique’ which bears a butterscotch-like honey colour.

Distinction between Copal and Amber

The biggest mistake you can make while buying natural amber gemstones is to place copal in the same category. Yes, copal is also derived from tree resins, but it is exclusively produced by the polymerization of aromatic ingredients of copal tree- Protium copal.It is often confused with the Caribbean Amber and the Dominican Amber due to the sparkling green red colouring.

While amber gemstones have an origin timeline dating back to millions of years, copal will be only a few centuries old. A radio carbon dating in lab establishes the age of the gemstones before tagging them for gem market.

 

World’s Least Heard Gemstones that Still Cost a Million

Wouldn’t you love to own something that can never be replicated or flaunted by anyone other? Here is your chance to actually own something that is not only rare but also rated among the least known gemstones in the world.

Grandidierite

Discovered in 1902, this gemstone is named after French naturalist and explorer, Alfred Grandidier. After 114 years of oblivion, grandidierite was first brought to limelight in 2015! Best quality gemstones are mined from Madagascar and Sri Lanka. A neo-silicate, it is relatively hard ranking 7.5 on Mohs scale. It has a typical bluish green colour with translucent appearance and fine rutile network. 

Jeremejevite

First discovered atop Mount Soktui in Siberia and Lake Baikal, Jeremejevite is found in small traces along with albite, tourmaline, and quartz. Other than Siberia, gem collectors have excavated the rare crystals in Namibia and Germany. It is a colourless gemstone with faint yellow and blue colour. Worth at $18000 per carat, Jeremejevite is linked to other rare mineral gemstones like Hulsite, Fluoborite and Sakhaite. 

Taaffeite

Named after Richard Taaffe, Taaffeite is an oxide mineral bearing greyish blue and red greenish shades. A very hard gemstone ranking 8.5 on Mohs scale, this gemstone is mined from the renowned mines of Ratnapura in Sri Lanka. Price tags hover around $5000 per carat, finding a Taaffeite is very rare. Spinel varieties are falsely sold off as this rare gemstone.

Musgravite

Musgravite exhibits red, mauve, blue, violet and grey colours.Rich in magnesium impurities crystallised within beryllium oxide in a trigonal system, it is closely linked to Taaffeite but was discovered at least four decades later in the mines located in Musgrave Range in South Australia. 1-carat Musgravite can fetch a price of $35,000 and more. In 2015, only eight recognised varieties of the gemstones were reported to have been extracted for commercial purpose.

Red Diamonds

Now we finally have a gemstone that everybody would love to adorn. But the price tag keeps it safe from the crowd! At $8.2 million per carat, red diamonds are not just the costliest gemstones but also the most alluring ones to feature in the list. Unlike other diamond varieties that have boron and nitrogen impurities, the red diamonds are pure in their composition. They are formed out of plastic deformation, which itself is a very rare phenomenon on Earth. 

Famous red diamonds to be ever cut by mankind is the 5.11 carat Moussaieff Red, which was earlier called the Red Shield Diamond.  Another celebrity name in the list of red diamonds is the 0.95 carat brilliant cut, round Brazilian Hancock Red which was sold off for a mammoth $880,000 ($926,000 per carat)!

Scapolite

It is definitely the one that only a handful of gem collectors actually know, and have seen in reality. Scapolite gemstone displays a fascinating play of colour along with fluorescence and Cat’s Eye effect. It is cut in cabochon to create exceptionally brilliant stone for jewellery. Popular varieties are Lavendar’s Cat eye and purple Tanzanian scapolite with per carat price of over $3000.

 

Black Gemstones You Never Knew Existed!

Considered as the powerful shadows of the brilliant coloured gemstones, the Black Stones are no longer kept in oblivion. Much like their colourful siblings, black gemstones too have a respectable fan-following. There are many black gemstones used in jewellery and healing, but we present you a list of those featuring in almost every charmer’s wish list.

Black Diamond

Heard about the 33.75-carat Amsterdam Diamond? Or the 312-odd carat the Spirit of de Grisogon! These are black gems.

Diamonds are available in almost every colour known to mankind. And yes, black is one of them. Though rare, black diamonds actually look like the other allotrope of carbon, the graphite. Black diamonds are actually called “Carbonado” and are tougher than the regular diamonds! It consists of traces of diamond, graphite and non-crystalline carbon.

Most geologists believe that carbonado diamonds are actually extra-terrestrialin nature dating back to 3.8 million years of space travel.For instance, Carbonado do Sergio has a meteoritic origin.

Black Opal

A fascinating variety of opal, Black Opals earned so much popularity that New South Wales- Australia proclaimed it as the official state gemstone! NSW is the world’s largest producer of Black Opals. Due to the small traces of iron oxide and amorphous carbon, some opals exhibit a unique trail of black. Black Opal set in bezel ring is considered as a protection from the evil forces.

The Halley's Comet Opal, a 1982-carat Black Opal is world’s largest uncut gemstone, priced at $1.2 million.

Black Beryl

Beryl is pretty common in nature, but when they appear in black forms they enter the list of rare gemstones. The black shade appears due to the insertion of microscopic black spinel impurities. They often appear as elongated prisms turning the transparent and clear beryl into greyish. The black opals are distinctly identified by their asterism effect, found in cabochon cuts. 

Black Sapphire

Sapphire is a legendary gemstone particularly recognised from its electrifying blue colour. But the black varieties are even more spectacular in their appearance. Symbolised as the stone of wisdom and confidence, Black Sapphire contains significant amount of aluminium oxide arranged in prismatic tubular and rhombohedral crystalline structure giving them their conspicuous star-shaped optical effect. 

Black Sapphires are very well received in the Arabia and Roman culture as an embodiment of fertility and love.

Black Star of Queensland is a 733-carat black star-sapphire discovered accidentally in 1960 in Queensland, Australia. 

Black Garnet

Also known as Black Andradite, it is absolutely hard to imagine that a flourishing red gemstone will also appear in a metamorphic form in black colour! The black garnets are actually a combination of three distinct crystalline structures- pyrope, andradite and melanite. A deeply spiritual gemstone, Black Garnet exhibits clairvoyant properties and heals the negative energy circles.

Other prominent black gemstones in the family that are equally sparkling and popular are Black Obsidian, Smokey Quartz, Black Tourmaline, Onyx and Serendibite.

So next time you shop for gemstones, don’t forget to pay special attention to the black family.

How to test Rubies: An Overview

Rubies are one of the rare and precious forms of gemstones, distinguished from the likes of emeralds and diamonds with its garish scarlet red colour. Meanwhile, market boasts of variety of ruby gemstone beads with primary hues ranging from yellow to blue to even purples! But nothing like the pale rose pink rubies that have ruled the hearts of Dukes and Emperors for centuries. 

How to tell if the ruby is real or fake? Here is what gem experts do to distinctly identify real rubies from the cheap imposters.

Primary Identification using Colour Consistency test 

What you see is what you get. Ruby is a blood red gemstone belonging to the family of corundum. The colour is present due to the chromium ions that inundate the crystal lattice largely containing aluminium oxide. If the colour is consistent with fine rutile impregnated in the crystal, it means the ruby is fine and untreated. If you miss out on the rutile, it means that the stone has been treated in heat to look finer and give a more consistent colour. A shade of imperfection is what makes rubies so attractive.

Test to find specific gravity 

Purest ruby corundum will bear a specific gravity of 3.98 with tolerance of 0.5% depending on the source of the stone. A special solution called “Clerici” is used to check the specific gravity of a ruby gem. Since the specific gravity of the dense fluid is 4.0, the rubies are supposed to float and displace the same weight of the fluid. 

Note: In market, rubies are available in the range between 3.95 and 4.05 specific gravity.

Test for Refractive Index

In terms of opacity, rubies can show transparency as well as translucency. The refractive index of a pure ruby is anywhere between 1.763 and 1.768 with dispersion measured under spectrometer coming at 0.018. Cheaper version of rubies and other gemstones have a much lower refractive index, often counted between 1.66 and 1.70. 

Double Refraction Test

Now we are taking serious science. Ruby gemstones do not boast of any particular line of cleavage. The fractures occur in conchoids or splintery manner. The hexagonal crystal structure of ruby and the internal fracture plane splits a single beam of light into two, leading to a phenomenon called Double Refraction. When observed under a polariscope, ruby exhibit birefringence or dispersion of 0.08.

Fluorescence Test

Rubies are exposed to florescent light and the refraction is checked with Chelsea Colour filter. Luminescence of rubies when florescent light is passed through them bears crimson or orange light. No other stone apart from ruby will give a red when exposed to florescent light. This is a key separation test between rubies and garnets.

Popularity of synthetic rubies

Use of synthetic rubies is not a taboo! They are imitation stones made by burning scarlet wool under the base. They were largely used to manufacture Ruby Lasers in the 60s. Red spinel, red tourmaline, Rubellite and Balas ruby are some of the names you should stay away as a buyer.

 

Top 8 World Famous Diamonds and their cuts

Diamonds are extraordinary gemstones. The most aspiring fact related to diamond is its origin and constituent- Carbon. Diamond is one of the rarer allotropes of elemental Carbon. Known to Indians for at least 6000 years, diamonds have always been an item to express pompous glory, love and magical companionship. 

Here is a list of world-famous diamonds, though lesser known to a regular gem buyer.

1 Akbar Shah

More popularly called as the Lustre of the Peacock Throne, Akbar Shah is a pear shaped light green diamond, now weighing 73.6 carat. Glorified by Mughal king, Shah Jehan, the diamond was lost in the trails of time when it was confiscated by Persian Emperor, Nadir Shah.  It returned back mysteriously in Turkey, with a new name- The Shepherd’s Stone. It was cut from 120 carats to its present weight by George Blogg and then purchased by Malhar Rao Gaekwad, ruler of Baroda.

2 Archduke Joseph 

A brilliant colourless diamond shaped in cushion form, Archduke Joseph now weighs 76.45 carat. Named after the Austrian duke, the diamond was mined from India’s Golconda wells. 

3 Argyle Pink Jubilee

The largest diamond to have ever been mined from Australia, Argyle Pink Jubilee actually has a flaw line that prevents its cutting into a shape. It weighs 8.01 carat.

4 The Black Orlov/The Eye of the Brahma

One of its kind, the Black Orlov is actually an item of massive importance to Hindus. It was stolen from the statue of Hindu god-Brahma, placed in a temple in Puducherry. The owner of the stone is ‘supposedly’ cursed and hence the 67.5 carat diamond is now displayed at NYC and London museums. 

5 Centenary Diamond

The love for big diamonds gets Centenary Diamond its ubiquitous positon in the list of world-famous collectibles. Discovered in 1986, the stone weighed a massive 599 carats. The gem now weighs 273.85 carats, with 247 facets. Its owner is unanimous, but continues to be displayed at major exhibitions. 

6 Darya-ye Noor

Weighing 182 carats, Darya-ye Noor actually means ‘Sea of Pure Light’. It is one of the largest and also the rarest diamonds to have ever been cut. It is a pink coloured gemstone was mined at the Kollur mines in India, and was owned by princely kingdoms of India till Nadir Shah looted it along with Koh-i-Noor and Akbar Shah.

Gemstone historians believe that the Darya-ye Noor and Noor-ul-Ain (both grace the Iranian Crown Jewels’ list) are actually cut out from the Great Table Diamond, once studded in the Peacock throne of Mughal emperor, Shah Jehan.

7 Graff Pink

Known to many as “one of the greatest diamonds ever discovered”, Graff Pink is a rare 24.78 carat gem boasting of an intense pink hue and priced at £29 million in its last auction.

8 Nassak/ Nassik Diamond

Now not many would believe that the Nassak is actually the same eye of the idol that lord Triamabkeswar adorned between 1500 and 1817. The pear shaped diamond now weighs 89 carat.

 

Adularescence Effect in Moonstones make them Priceless

Milky white gemstones with colourful sparkles symbolize the love for translucent dazzlers. Yes, glassy and clear gemstones like diamond, garnets, rubies, sapphires and emeralds remain the top eye-catchers. But there is a certain attraction that makes opals, moonstones and agate very popular. The optical phenomenon of adularescence is what renders these gemstones their enticing beauty.

What is an adularescent gemstone?

Crystals exhibiting the Schiller effect are called as adularescent stones, which is very similar to the labradorescence and adventurescence. Adularescent gemstones exude a milky and bluish glow originating from the diffused structure within the crystal. The schiller seems to move within the stone, and hence gives an effect of light source moving as well. Orange and blue lustres are commonly seen in the gemstones. 

Why adularescent? 

The name ‘adularescence’ is derived from the gemstone called Adularia. Adularia itself derives its name from the location where it was first discovered. Adularia is orthoclase potassium-enriched feldspar found in Adula Massif, Ticino (Tessin), Switzerland in 1780.

The degree of schiller effect in the gemstones other than Adularia is a highly varying and hence remains a scattered phenomenon. In non-Adularia gemstones, schiller effect appears along with ‘girasol effect’and opalescence. Some gem experts like to connect adularescence with indistinct bands of chatoyant effect. In other words, adularescent gemstones are likely to showcase cat’s eyes effects and asterism.

Adularescent Moonstones

Labradorescence and adularescence are related terms as afar as optical phenomena are concerned. Both of them are seen in moonstone Gemstone and Labradorite in equal intensity. The similarity arises due to their origin from feldspar. 

Moonstone has two feldspar minerals in it- orthoclase and albite. Adularescent moonstones exhibit intermingling of the minerals and result in a new ingrown stacked in alternate rows. The light scatters randomly between the thin lines and layers causing a blue sheen. When the moonstone gemstone beads are viewed in different angles, the misty light also rolls in action.

How to check for a real Moonstone

Moonstones are approved of their originality by checking three factors:

 

  • Background colour
  • Surface colour
  • Sheen orientation 

 

The adularescent gemstones are semi-transparent and colourless, with sheens bearing shades of blue, silver and rose. Rainbow moonstone show multiple colours like green, yellow and brown-grey. In terms of pricing, brighter the shade, higher will be the cost. High valued moonstones exhibit a 3-dimensional depth in blue shade. Blue moonstones necessarily command a higher price than milky and transparent adularescent gems.

How cut makes a difference?

Moonstonesare often shaped in the beads and balls, stranded in necklace and bracelets. The adularescent moonstone is cut in cabochon that multiplies the sheen and clarity of the colours. Oval moonstones cut in cabochon remain top collections, apart from the Fancy Cut and Point cuts with square base. 

For uniform adularescence effect, moonstones are never given a long flat base. They diminish the effect and also take away the sheen and clarity. In short, flat based moonstones are not as attractive and glittery as the cabochon ovals.

Star Gemstones: Asterism in its Enticing Glory

Mankind has always been drawn to the mystical skies shinning with uncountable number of stars. Since time immemorial, numerous artworks have been inspired by the stars and planets twinkling. And when someday, gemstones with starry dazzle were discovered, it meant owning the stars. Meanwhile not all gemstones known to man exhibit the starry dazzle and it is an exclusive phenomenon. But why is that? That’s because, it is an optical property based on the crystal structure.

What is the phenomenon called?

The property is called asterism. Asterism is an optical phenomenon that occurs sparingly in some gemstones. When the light beam passes through the crystal, it showcases star-shaped figure. In astronomy, asterism is defined as a pattern of stars. It is very different from what we know as a constellation. Asterism is a pattern of stars or constellations which may not be recognized in any form. 

Types of Asterism

There are two distinct types of asterism exhibited by the gemstones found naturally. They are:

Epi-asterism

Seen in sapphire gemstone and garnet beads, epi-asterism is caused due to the reflection of the light along the parallel planes formed from inclusions/ rutile within the gem crystal.

Di-asterism

Commonly seen in the Rose Quartz, the phenomenon is seen when the light source is behind the stone. The phenomenon is seen in crystals with milky and opaque appearance. 

In short, di-asterism in gemstone is caused by a transmitted light, while epi-asterism occurs due star formation from a reflected light beam. Diffused light sources don’t form star shapes in the gemstones.

Asterism in Sapphires

The first instance of gemstone asterism was discovered by the Greeks. The cuts necessarily enhance the phenomenon. For example, star sapphires cut in cabochon display six-rayed star pattern. Other stones that exhibit the property are rubies, topaz, chrysoberyl and moonstone. The presence of titanium oxide particles, called rutile, gives the gemstones their trademark asterism. 

Gemstones with asterism have always been linked to folklore and superstition. They were believed to ward off evils in the dark and keep the faith strong. Star Spinel, garnet, Diopside and sapphires were specifically cut to enhance the healing properties of the protective gemstones. 

Asterism in Quartz

Pink and red quartz exhibit asterism that occurs due to transmitted light. Citrines also reveal asterism when heated to a certain temperature. The heating dissolves the finely lined rutile particles an align them to form stars. Round cut quartz are known to showcase exciting play of star formation, with interesting planes. 

Asterism in Synthetic gemstones 

Synthetic corundum is aluminium oxide which is largely produced to replace diamonds in cutting and abrasive tools. The asterism is seen in corundum gemstones.

Commercial influence on Star gemstones

Asterism is a key commercial feature that makes the gemstone look rarer in the market. Star beryl and star spinel gemstones are anyways rare, which are complemented with immaculate cuts and shapes. Star gemstones too have to meet the 3 C’s parameter to qualify as precious item: Colour, clarity and Carat.