Precious gem stone
According to The American Geological Institute, a precious gem stone is defined as:
"A gemstone that, owing to its beauty, rarity, durability, and hardness, has the highest commercial value
and traditionally has enjoyed the highest esteem since antiquity; specifically, diamond, ruby, sapphire, and emerald
(and sometimes pearl, opal, topaz, and chrysoberyl)."
Semi Precious gem stone
A semiprecious stone is defined as:
"Any gemstones other than a precious stone, or any gemstone of lower commercial value than a precious stone;
specifically, a mineral that is less than 8 on the Mohs scale of hardness. A gemstone
may also be regarded as semiprecious because of its comparative abundance, inferior brilliance, or unfamiliarity
to the public, or owing to the whims of fashion. This arbitrary classification is misleading, as it does not recognize,
for example, that a ruby of poor quality may be far less costly than a fine specimen of jadeite."
There was a time when the boundaries between precious and semiprecious stones were clearly defined. Diamonds,
emeralds, rubies, and sapphires were considered the precious stones and all others fell in a class below them.
This has not been the case for some years, and today gems are evaluated by a different criteria.
- Beauty
- Rarity
- Durability
- Desireability
The above qualities now determine the overall class and value of gemstones.
Gem stone beauty
This, of course, is open to much discussion since the saying "beauty is in the eye of the beholder"
is true. The beauty of a gemstone can vary widely, depending on whose opinion is being voiced. This is a good reason
to decide what is beautiful to you, and choose gemstones for your collection that are pleasing to your own
eye.
Gem stone rarity
To determine the rarity of a stone, you must take into account the mineral group, it's quality, and the source
of the stone. For example, not all emeralds are considered rare due to the fact that there are still large deposits
of emeralds available throughout the world. Emeralds of excellent color and proportion are very rare and collectible,
commanding many thousands of dollars.
Some of the rarest gems on the current market are the formerly called semiprecious stones. Examples of this
are watermelon tourmaline, black precious opal, and natural alexandrite. These stones can be hard to find in good
quality and you will discover they are quite expensive to acquire.
Gem stone durability
Durability should take into consideration the ability of the stone to withstand wear and also how practical
the stone is for its intended use. Most gemstones are made into jewelry and must withstand being rubbed, dropped
and knocked against hard objects. The stronger, harder stones will continue to sparkle much longer than their metal
settings.
There are many very beautiful stones that appear to be good candidates for jewelry but in fact are easily damaged
and nearly impossible to cut because of the structure of the crystal. The Moh's hardness scale is the accepted
gauge for determining a stone's overall durability.
Gem stone desireability
Even within the same type of gem, not all gemstones are equal. There is a huge variance that can result in one
stone being graded gem quality and its similar 'cousin' being labeled industrial quality.
The diamond is a good example of this. Some diamonds are only suitable for industrial use (80% of all diamonds
produced) and others command tens of thousands of dollars as gem quality stones. This phenomenon exists throughout
every mineral group. Today, a quarter carat garnet of exceptional beauty and quality can be worth far more than
a 3 carat emerald that contains heavy inclusions (foreign matter).
The rank of precious or semiprecious gem stone is determined by taking into consideration the stone's
beauty, rarity, durability and desireability.
Some of these things change with fashion, or the availability of stone deposits. The operations of various mines
in different parts of the world can be subject to political and other factors. Gemstone values change periodically,
which makes gemstone collecting all the more an exciting adventure!
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