Initial concepts

Gems: any material with a suitable combination of attractiveness, durability & rarity, & intended for use in jewellery or adornment, esp. if cut & polished.

Gem materials: broader term. All gemstones, naturally formed as well as artificial, products in jewellery.

Gem stones: formed by nature, without human interference. Not artificial - which is partially or entirely manufactured.

Most valuable are precious then semi-precious. These terms have loose associations so are no longer used as they can give the wrong impression of relative values. Imitations can be very realistic. Need to be wary of stones larger in size than expected or with excellent colour and clarity. Beauty, rarity and durability are what make the up the core of a gem's quality but there are other factors including colour, how it has been cut & shaped, lustre and it's dimensions (larger often seen as better).

Gem quality? Some materials, usually considered highly prized does not always occur as gem quality. Many diamonds mined from particular deposits are not suitable for cutting as gemstones for jewellery and therefore can be used industrially instead eg: for polishing and cutting tools. In the Australian Argyle mine, famous for pink diamond, much of the yield at times was not suitable for cutting. Only 5% may have been gem quality and about 40% called near-gem quality. Only a small amount was useful for gems. The usability is dependent on manufacturing or cutting costs and the overall economies.

Beauty

Strong colour can be visually or emotionally impactful. A certain cut can be facinating (diamond) and play-of-colour captivating (opal). Each gem has its own characteristic giving individual appeal and desirability. Some inclusions may spoil a stone's transparency or make it more beautiful and valuable.

Some gem material may be too rare for use in commercial jewellery, too difficult to cut and polish (due to physical properties) or too soft or unstable to withstand natural wear. But these can still be prized by collectors and museums in their own right. Collectors gemstones' are an important niche in the trade. These stones can sometimes fetch high prices.

Rarity

A fundamental aspect that increases desirability. Human psychology - the unobtainable is more desired.

Gem traders originally sourced gems for royal / wealthy as they could afford them. They often came from remote places and travelled along the trade routes eg: Indian diamonds found in Roman rings in Italy, emeralds from Columbia and rubies from Burma (now Myanmar). Some localities are known for producing the best stones so that will increase the value of those items eg: Kashmir renowned for 'silky' sapphires.

Size - generally the greater the size the greater the value but a smaller gem from a particular locality may be rarer and therefore more valuable than a gem from elsewhere. Also consider colour eg: a small ruby of exception colour may be more valuable than a larger ruby of poorer colour.

Facotrs affecting rarity therefore include origin, size and colour.

Durability

The capacity to withstand wear and retain its appearance, preferably for generations. Value and desirability decrease if the material degrades, fades or wears out quickly.

Many physical properties that will determine durability.

• Hardness - resistance to scratching.
• toughness - resistance to force / blows. Eg: peridot, beautiful yellow-ish green gemstone, relatively soft and cab be found in older jewellery that will show scratches and chips.
• stability - A) exposure to light may result in fading eg: some amethyst loses its deeper purple if left in the sun. B) chemical some gems are susceptable to chemicals eg: solutions used in jewellery, workshops or house cleaning products.

Value

Availability and demand ratio play a key role in addressing value. Market availability - how many gems are available and controlled for example by the mining output Demand depends on desirability, which relates to fashion trends, cultural factors and spiritual beliefs. Eg: Jadeand jade-like materials in China more than Europe; natural pearls in the Arabian Gulf.

Three large groups on the gem market today - diamonds, coloured gemstones and pearls [the course not addressing biogenic gem material such as coral or ivory]. The trade refers to all gemstones that are not diamond or pearls as coloured gemstones. A collective terms to include almost all coloured gem material eg: rubies, sapphires, emeralds, topaz, tourmalines, garnets. Also gem varieties that may be colourless like rock crystal or colourless sapphire.

The International Coloured Gemstone Association unites traders around the world.

Value factors include visual and non-visual:

• natural/artificial/synthetic
• treatments - any treatments along with geo'l origin are usually expressed in gemmological reports produced in labs
• colour
• clarity
• cut - how well is it cut to promote the colour and clarity?
• size / weight - carot weight. Value will increase with size. Price per carot will increase value as rarity itself increases value and its often harder to find a larger gemstone even if its comparable in colour and clarity.
• documented history - provenance; was it worn by royalty or celebrities; (where did it come from and where has it been since)
• perceived beauty
• rarity
• durability
• lore

For cut gemstones:

• colour - vivid and intense, uniformly distributed
• clarity - absence of visual impurities and flaws
• cut and polished with skill

Geological origin - confirming the country of origin is a debated topic. Even with complex analytical equipment and a large reference collection , origin determination is an opinion.

Provenance example: who has owned the gem? eg: large, pear shaped natural pearl (26x18mm) set in a diamond and silver pin, at auction at Sotheby's Geneva 2018, went for $36.1 million. It was owned by Marie Antoinette and was expected would go for $1-2 million.

Provenance example: Argyle pink diamonds. Argyle mine in W.A. is famous as a supplier of the largest pink diamonds. 90% of world's supply. Was in operation from 1983-2020. The market value is affected by the decreased offer of these small pink and red diamonds. The perceived scarcity will affect demand. The can also be found in Russia, Brazil and South Africa but there is no indication that another source with a similar production as the Argyle mine will be in operation soon.

A visual examination of a stone may not be enough to value it but experience in gem'y will help you gain knowledge in helping to established value.

Precious or semi-precious

Precious: historically diamonds, rubies, blue sapphire, emerald and natural pearls have been the mmost highly valued and more frequently desired therefore called 'precious stones'

Semi-precious: due to the decreased value and popularity most other gemstones were called 'semi-precious'.

These terms are still in use but the World Jewellery Confederation (CIBJO - which establishes the gem and jewellery trade nomenclature) disapproves of the terms - state them as erroneous and obsolete trade expressions. For eg: a poor quality blue sapphire is of less value that a fine quality tanzanite (violet blue to blueish gem from Tanzania). The definition of a gemstone is not necessarily related to a higher or lower market value and therefore the terms precious or semi-precious are synonyms in the trade.

Natural substances

Formed in nature without human intervention - collectively called gemstones. Include many minerals (eg: diamond, topaz, quartz) rock (lapis lazuli) and fossils (amber).

Rough (unfashioned state) or ornamental (jewellery/carving/inlays/architecture/art) or biogenic (results from the activity of living organisms). No definite line between gem materials used in jewellery or for ornamental purposes - beautiful material will be used for both. eg: still life brooch of a cicada in Jadite.

Meteorites: some are used as gem material. Most notable called a pallasite, containing olivine ('space' peridot), which is also found on earth. Eg: meteor called 'Esquel' found Esquel, Patagonia, Argentina. Samples sometimes seen in the trade as polised slabs containing the gem peridots within. These are also cut as gemstones and traded as extraterrestrial gems eg: Lybian Desert glass used in ancient jewellery.

Biogenic:

• produced by living organisms. Until only recently the term 'organics' was used for gem material of a biological origin & included material having undergone a geo'l process eg: amber, ammolie & jet.
• term 'organic' has other meanings in chemistry or the food industry so to remove ambiguity in the jewellery trade the term 'biogenic' was agreed upon by CIBJO. Term organic is still used for gems composed of organic matter or organic molecules as defined in chemistry
• best known are pearls (produced in molluscs), amber (fosillised resin), jet (fine and black, believed to be foss. wood), decorative shell (used in jewellery and the decorative arts).
• also seen in jewellery inc. mother-of-pearl, coral, ivory, tortoise shell, horn, bone, antler, wood (ebony), hair.

Coral:

• soft, Mohs 2.5-3.5 and easily attacked by acids.
• Collective name for more than 7000 species of marine creatures but only c.10 have the classification of 'precious coral' by gemmologists and jewellers. These occur in different ecosystem than the endangered reef coral and are harvested in deeper water, below 50mts.
• Red Mediterranean coral has a long history of use in jewellery eg: Angel's Skin variety discovered in 1800s (rare). Although not endangered some are subject to international trade regulations eg: CITES.

CITES:

• CITES regulations - Convention on International Trade in Endangered Species of Wild Flora & Fauna / The Washington Convention.
• Some biogenic material is strictly regulated to ensure sustainability and responsible sourcing. Cannot be traded for commercial purposes.
• CITES lists a few gem materials because they are 1) endangered or 2) need special protection to avoid becoming endangered. 1) eg. ivory from elephants and whales, tortoiseshell from sea turtles, rhino horn. 2) eg: blue reef coral, narwals or hippos. CITES also in place to monitor trade eg: includes some Asian precious coral species or walruses.