Here, we are discussing about evaluation of colored stones as loose gemstones or in cut form. How faceted stones or loose gemstones for sale should be analysed while buying. What are key factors that a gem buyer should keep in mind before making final purchases of the stones which are already cut or faceted, being ready to fix in the jewelry. There are many key points about setting pricing or value of a stone. Some of the popular factors, defined by gemologists and trade gemstone dealers, are listed below. They are
Following chart is indicating the importance of these factors in percentage.
1- Color
Color is always considered as a “ king “ in the colored stones. There are some dimensions in the colored stones regarding their color evaluation. Those are
hue (yellow, green, red, green, blue, etc)
saturation (intensity of a color)
and tone (lightness or darkness)
uniformity of color
The optimum color range of each stone is different. Pale colors usually have low value. Though pale green colored stones from Afghanistan and Pakistan such as tourmaline is high demanded stone. Gemstones get color by inclusion of specific trace elements in them.
elements’
Role in color variety:- Titanium Blue Vanadium Green / Color change Chromium Red – Green Manganese Pink Iron Red – Green – Yellow Cobalt Blue Nickel Green Copper Green – BlueColor of the stones should be open. Darkest tone of the stone gives lower value to the stone.
Open color is a market term used by gemstone dealers. Open color means tone of the color. How much the stone is dark or light in the color. Darkest shade of the stone made them less in value as they go close to the blackish tone side. In colored stone, it is the color only that define the value of a stone.
2- Clarity of the Colored Stones
Clarity in colored stones Indicates about internal and external quality. We can judge the clarity by looking into external appearance and internal flaws of faceted stones. External appearance is judged by pointing out flawless surface on table, pavilion or on facets. Internal analyses tell us about inclusions inside the stone.
Is it having flaws inside like inclusion or cracks? What type of and how many inclusions the stones have ? Is it completely Flawless?
Stones are divided into following scale of clarity.
inclusions cannot be seen without magnification
Inclusions in the colored stones | Loose Gemstones
Some gemstones are having inclusions always. Some are commonly eye - clean. Sometime inclusions increases the value of a stone. Such as Kashmir Sapphire's resulting velvet appearance that occurs due to internal inclusion which gets light reflection.
Star Sapphires are another example. Inclusions cause star in sapphires, rubies or tripeche in emeralds. Star sapphires are also expensive in the market if they are in fine quality. Sometimes, the stones have unique and rare inclusions. Such type of inclusions is also acceptable by the gemstone dealers. Such pieces are sold to gemstone collectors. Sunstone is another example of beautiful inclusions. Cats Eye stones also reflect beautiful eye light moving brilliance that is caused by internal inclusion and light reflection to the inclusions.
Some gemstones are not cleared which are cut into cabochons or tumbled. They are most of the time opaque.
3- Size & Weight of Colored Stones
Size of the gemstone is another evaluation point of colored stones. The other element for evaluation of the stone is size. What is size of the stone ? 1carat, 2carat, 4carat. The more the stone will be big in size, the more it will be pricy. The more the stone will be small in size, the more it will have lower price.
Size also depends on demand type. If someone is making jewelry in such designs where equal small size calibrated stones are requires, there calibrated mm size stones are fixed.
There are many calibrated stones in mm size which are pricy per carat such as rainbow sapphires, emeralds in mm size to be fixed in watches like Rolex or rubies. The cutting of small size colored stones in mm scale is very very difficult. They will be highly expensive if cut in round diamond cut or round brilliant cut.
4- Cut of Colored Stones
Cutting of colored stone is exactly as important as other characteristics are important. A good and fine cutting of any bad rough stone can make it worthwhile. Whereas bad cutting of any exceptional good rough stone can lower the value of a stone after cutting. The more the stone will be in fine cutting with good and equal facets, the more price will be low.
Evaluation of gemstone cutting involves five major factors. Those are below mentioned.
Stones are evaluated by shapes also. Demand of specific shapes and cutting styles of colored stones is changing day by day. They have evolved to that in different type of shapes which are here.
The popular gemstone shapes are ovals, round and emerald cuts. Pears and Marquises are less desirable shapes in the colored stones. They are traded about 10 to 20% less than oval shapes of same quality. However, the shape of cut stone depend on rough stone shape also. In order to save weight, rough stones are cut into similar shape.
There are some gemstones which go for only specific shapes such as tourmaline, emeralds due to their specific hexagonal crystal structure. If we will cut them into oval or round shape, we will loss maximum weight after cutting. Mostly emeralds and tourmaline is cut into emerald cut, square, or octagon shapes.
The faceted pattern is a subjective choice which is also called a cutting style of the gem. The brilliant crown and step pavilion is a market standard for sapphires and rubies. Emeralds are cut into step cutting.
Faceted cutting is done to gain maximum brilliance in a symmetrical manners. Symmetry of the cutting is very very important. There are two parts in faceted gemstones which are Crown and Pavilion.
Crown of the stone Pavilion of the stone
Crown:- Crown is meant to catch light. It creates scintillation.
Pavilion:- Pavilion's job is to create both scintillation and brilliance.
Low crown will create low sparkles in the gemstone. The gemstones having shallow pavilion will have lot of windows. There should be symmetry in both. less crown with deep pavilion will increase the weight of the stone but size will be small. Big Crown with less pavilion will not let the stone fixed in ring or other jewelry settings. It will increase the size of the stone. There should be symmetry in crown and pavilion of a stone.
Fine cut gemstone will catch our eyes immediately. Symmetry of stone is done by creating equal proportion of the cutting. Some types of bad symmetry of cutting or faceted gemstones are here below:-
5- Finishing of the Stone
The final touch comes to polishing of the stone. After good faceting, polishing of stone matters a lot. Final touch also refer to fine tuning of facets, polishing
In defining value of faceted gemstones, location of the stone also matters a lot. In fact stones are priced according o region. In blue sapphires, Kashmir sapphire is a standard due to its specific geological occurrence in a specific geological location. Burma Spinels and Burma rubies are popular in rubies and spinels. Paraiba tourmaline is popular for Brazil Paraiba tourmaline.
Lapis from Afghanistan, Peridots from Pakistan, Aquamarine Crystals from Pakistan, exceptional quartz varieties from Pakistan, Kunzite from Afghanistan, Swat Emeralds from Pakistan, Australian Opals, Ceylon Sapphires, Brazilian Amethyst, Citrine are popular due to their locations and origin.
Treatment of the stones affect the pricing of cut stones. Natural stones are highly demanded. They should be without any kind of treatment. There are different types of treatment in the market. Heat treatment is the most popular treatment for many gems.
Standard heat treatment is acceptable in the market. However, beryllium heated stones like red or orange sapphires is not counted as normal heat. Other treatment like filling fractures by wax in turquoise, glass in sapphires and rubies, oil in emeralds is highly discouraged by the gemstone traders in the market. Some sapphires and rubies are glass filled in cabochon form. Some emeralds are treated with resin, wax or green oiled which is extremely not acceptable in the market. Baby oil in emerald is acceptable which can be even removed by acetone. Baby oil is put into emeralds in rough in order to avoid frictions.
Precious stones have more value than semi precious stones. Precious stones include sapphires, rubies, emeralds normally. Semi precious stones include peridots, amethysts, topaz, garnet, citrine, quartz etc.
Trends in gemstone and jewelry industry define the price of the stone. The birthstones are more demanding stones in a particular month. Wedding season normally comes from September to March. In this season, engagement and wedding rings are sold than other days. Engagement rings normally include diamonds, sapphires, rubies, emeralds, amethyst, spinels, rare garnets, imperial topaz, morganite, paraiba tourmaline, bi color tourmaline, peridots or some rare semi precious stones such as color change stones.
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