Gemstone Jewellery
Gemstone jewellery contains a vital energy enhanced by precious metals. Gemstone jewellery positive influence on a human wellbeing enhanced by precious metalshas been known since an Ancient Egypt, where a different gemstone was assigned to each month of the year, also known as birthstones.
What are Gemstones?
A gemstone or gem is usually cut and polished piece of attractive mineral used in making Gemstone jewellery. But it's important to notice that some gem stones are not minerals, but rocks (such as lapis-lazuli ) or organic in nature (amber or jet).
Gemstones Characteristics and Classification
The value of the gemstones will depend on characteristics such as hardness and rarity, but soft gemstones also can be used in gemstone jewellery production depending on a stone aesthetics value, such as lustre.
It's very common to call some of the gemstones as precious or semi precious. The division is quite arbitrary, mainly based on fashion trends which have changes quite often in the last few hundred years. Today diamond, ruby, sapphire and emerald are considered to be precious stones.
Gemstones can also be classified into different groups or species, and varieties.
Each gemstone group shares a common crystal structure or/and chemical composition, for instance Beryl, Corundum, Feldspar, Garnet, Jade, Opal, Quartz, Zoisite are some of the best known groups.
Each group or species may have subgroups or varieties. Emerald, aquamarine, bixbite, goshenite, heliodor and morganite are varieties of beryl and have completely different colours.
Gemstones are also categorised in terms of:
Gemstones Treatments
Some of the gemstones are often treated to enhance the colour or clarity. The treatment can affect the value of the stone depending on the treatment, it's extend and the stability of the stone after treatment.
Heat treatment can improve gem stone colour or clarity, for example most of citrine is made by heating amethyst, and much aquamarine is heat treated to change the yellow or green tones into blue or enhance an existing blue colour.
Radiation
The beautiful lighter and the darker blue shades of blue topaz are achieved through the irradiation that changes the colour from white to blue.
Most greened quartz is also irradiated to give it the yellow-green colour.
Waxing and Oiling
Some stones, for example, Turquoise and Emeralds, tend to have natural fissures that sometimes are filled with wax or oil to disguise them. The wax or oil are also coloured to make the gem stones to appear of better colour and clarity.
Fracture Filling
Fracture filling is used with different gemstones such as diamonds, emeralds, sapphires and rubies. The treatment involves a filling of surface or internal fractures with a foreign substance to improve a gem stone appearance. The treatment is inexpensive and produces a visually more appealing and apparently valuable gem stone.
Synthetic Gemstones
Synthetic gem stones are manufactured to imitate other gemstones. For example, cubic zirconia and Moissanite are synthetic diamond imitations that copy the look and colour of the diamonds but possess neither its chemical nor physical characteristics.
Artificial Gemstones
Artificial gemstones are lab created and are not imitations. Artificial gemstones will possess identical chemical and physical characteristics of the natural stone and will have a more vivid colour due to lack of impurities. However, natural gemstones are still considered more valuable than artificial gemstones due to their relative scarcity.
Examples of artificial gemstones are diamonds, ruby, sapphires and emeralds.
Gemstones Cutting and Polishing
Gem stones used in jewellery making are usually cut and polished. There are two main types of Gemstones:
cabochons- smooth, dome shaped stones, such as opal, turquoise, variscite. These gems are designed to show the stone's colour or surface properties. The surface of the stone is grinned, shaped and polished using grinding wheels and polishing agents.
faceted- cut with a faceting machine at regular intervals at exact angles and used on transparent gem stone to maximise optical effects such as light reflection and sparkle. The stones can be cut into any known shape depending on the optical properties of the stone.
Gemstone Colour
The colour of the gem stone will depend on a way the day light is absorbed when it passes through the stone.
The day light has a colours spectrum from blue to red. Gem stones tend to absorb some of the light and the shade of the spectrum reflected will give the stone its colour. A ruby appears red because it absorbs all the other colours of white light except red.
Despite the fact that different varieties of the same stone have the same chemical composition, the colour exhibited can be completely different- every now and then an atom is replaced by a completely different atom (impurities) causing the stone to absorb certain colours and leave the other colours unaffected.
Some gemstone treatments use this fact to manipulate the colour of the gem.
Gemstone Valuation
There is no universally accepted gem stone grading system apart of diamonds, which are graded using GIA system developed in early 1950. The system is based on 4C's (colour/clarity/cut/carat) and uses X10 magnification for standard clarity grading. The rest of the gem stones are graded using naked eye.
IGI, GIA, AGS, American Gem Trade Laboratory, AGL, EGL, GAAJ, GIT, AIGS, SSEF, Gübelin Gem Lab are international laboratories that grade gem stones. Till recently each one of the above bodies used its own methodology in gemstone grading which led to an establishment of the Laboratory Manual Harmonisation Committee (LMHC) that aims at the standardisation of wording on reports of each one of the laboratory, but the differences do still exist.
What Makes Gem Stone Valuable?
Physical characteristics that make a colour stone valuable are:
Colour
Clarity -to a lesser extent
Optical phenomena-interaction of light and matter, for example colour zoning (uneven distribution of colour within a gemstone)
Asteria -star effects
Water- combination of colour and transparencyfirst water=gem of the finest water, second water, third water,byewater
The value of the gem stone is also affected by the fact if they are considered to be precious or semi-precious stones. This will depend on culture, fashion trends and the stone rarity. For example, up to the discoveries of bulk amethyst in Brazil in the 19th century, amethyst was considered a precious stone.
