Jan/Feb
2013

Buying Rocks

Written by Barbara Hight-Randall and Marlene Petersen
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buying-rocksDo you find buying gems confusing? Check out these tips from Certified Gemologist Appraiser Barbara Hight-Randall.







CLARITYclarity
Clarity is the integrity of a crystal, its internal, naturally occurring imperfections. It tells us the stone came from the earth, not a laboratory.

There are five considerations for clarity: size, number, location, color and nature of the imperfections—big versus small, colorless versus dark, few versus many, close to the edge versus deep in the stone and an included crystal (i.e., inclusions) versus a break in the stone. The number of internal characteristics a gem has affects durability, beauty and passage of light through the stone.

The emerald on the left may have perfections but they are not visible to the naked eye. If you look closely at the stone on the right, you will see a large break in the middle of the stone, which detracts from its beauty, interrupts the passage of light through the emerald and makes it less valuable.

Tip on Clarity:
Always ask the jeweler to demonstrate a stone’s clarity under a magnifying glass. There may be microscopic imperfections that are affecting its price.

 

cutCUT
Both pictures on the left are the same eight carat, yellow sapphire.

The top one is beautiful and very valuable, but if you look closely, you can see right through it. The gem is “windowing.” There is nothing wrong with a gem that windows, but it should cost less than one with similar characteristics that doesn’t.

“When you look into a gem,” says gemologist Barbara Randall, “you should see a pool of light with no end.”

Compare the picture on the bottom. This is the same sapphire as the one on the top, but it has been recut. This new cut allows more light to refract throughout the gem, so all you see is color, depth, richness and fire. The stone is more valuable now because the cut is a work of art and enhances the inherent properties of the sapphire.

Tip on cut:
Buy the best cut you can afford, even if it means buying a smaller gem. A good cut will enhance the properties of the gem.

 

carat-colorCARAT AND COLOR
Carats are the weight of a gemstone (not to be confused with karats, which are a unit of purity pertaining to gold, 24 karat being the purest). One carat equals 200 milligrams. Large gems are rare, and rarity drives price, so generally, the higher the carat weight, the more you will pay for the gem.

But bigger isn’t always better. The blue sapphire (top left) has a greater carat weight but costs less than the one pictured below it. That is because of color. Sapphires that are nearly black, like the one on top, are much more common and, therefore, less valuable. Also, its color falls flat in the center (i.e. extinction) compared to the one on the bottom, whose color looks like an endless, deep blue velvet pool.

Carat Trivia:
For every one carat diamond sold, a jeweler typically sells over one million smaller diamonds, making the sale of a one carat diamond one in a million.

Tip on Color:
Hue, tone and saturation of color dictate the rarity of colored gemstones, so look for the richness of a rainbow when shopping for them.

 

WHITE DIAMONDS

Unlike colored gemstones, colorless diamonds are rarer than body color, and therefore more valuable. The more brilliant the diamond—i.e. the amount of white light it creates—the better. When a diamond is cut properly, light goes in, bounces throughout and comes back out the top to create more white light. A good cut can even create a whiter looking diamond than is inherent in the crystal. Cutting the diamond for maximum light performance, can pump out more brilliance, make the diamond look larger, reduce body color and have potentially fewer visible imperfections.

Diamond Trivia:
For every one carat finished diamond, you need a two carat rough crystal because half the total weight of the diamond crystal is lost when it is cut.

Tip on diamonds:
You will get more diamond for your dollar on a diamond whose color has been enhanced by the cut verses one with intrinsically perfect color (which is extremely rare, thus far more expensive).

 

Final shopping tip:
Find a knowledgeable jeweler and have her show you gemstones with the different attributes, discussing what is important to you and how that affects price. Making comparisons is the key to knowing which gem is for you.