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To understand why the fissures or the cracks in precious stones are filled, we first need to understand the effect that fissures have on gemstones.

But before this I am going to explain a very important concept to you about gemology: THE REFRACTIVE INDEX.

The refractive index (also called the index of refraction) of a gem concerns the relationship that exists between the speed of light in a vacuum (whose index is 1) and the speed of light through the gem. The denser the gem, the lower the speed of light in that medium and the higher its refractive index. Usually gems have a RI from 1.2 to  2.6.

But now let's get back to fissures; certain gems, such as emeralds, usually present quite a few inclusions, and inside these inclusions we find fissures and/or cracks that can break through to the surface, and then, what happens to light? This is when what we call reflexion takes place. Light meets two different mediums; in one it travels at one speed, and in the other at a different speed; and the difference is so large that it becomes very visible.

I’m sorry, but I had to say it. THEY DON'T EXIST. The same as semi-good friends or semi-tasty food doesn't exist. Imagine that your son/daughter comes home one day saying:  “mum, dad… I semi-passed the exam”.  What would you think?

From among all the weight units, the most commonly used is CARAT, a word that derives from the Arab word KIRAT, the weight of the carob tree seed, which was used as a measurement unit because the seeds’ weight was always the same.

CARAT

•       It is the weight unit usually used for precious stones.
•       Equivalent to a fifth of a gram: 1ct = 0.2 g = 200 mg
•       These days the carat metric is used in all countries.

The weight in carats of precious stones must not be confused with the number of karats as an expression of the GOLD GRADE (quality index that expresses the amount of fine gold that a certain jewellery piece contains).

24 karats =  100%  //   18 karats  - 75 %.

 12 steps about how to buy loose gemstones online.

• To find the proportions of a stone, you need to see at least three photographs of the same gem - in one photograph you should see the crown, in another the pavilion and in the third you should see the girdle. This is the only way to get an idea ....

1. GEM CONCEPT

 A GEM IS A NATURAL PRODUCT with some specific characteristics:

BEAUTY. It’s a personal concept. If the gem is beautiful for you and makes you feel beauty, then, that’s your gem.

Beauty is related with the visual sensation: color, brightness, clarity….

RARITY. A gem is a nature miracle. Depending on its exclusivity this will be its price.

DURABILITY. It has to be transmitible, inheritable. Consequently it is very important the hardness, the exfoliation and the resistance to certain processes or products.

2. RARITY

Rarity means exclusivity. If you want to own a gem that few people have, you will have to pay for it.

Rarity is about the amount of this gem in market either by the low production of it in the nature or else by the difficulty in extraction and handling.

3. THE IMPORTANCE OF HARDNESS

Air contains particles of silica, with Mohs scale hardness 7.

Any stone with lower hardness than 7 is subject, over time, to become scratched on surface or chipped in the edges. As a result of this its brightness will be reduced. In this case you’ll have to provide an special treatment.

4. THE USE OF A GEM

The convenience of one gem or another will depend on the use there of and how often is going to be worn.

 You need to be conscious of the damage a gem suffers due to the daily use.

Earrings don’t suffer the same as rings do. A special-ocasion gem doesn’t suffer the same as an every-day sleeping-with gem.

You have to consider the weight of earrings with big gems

THE FOUR FAMOUS “C”. THE CLARITY

CLARITY: Clarity is the second most important factor.

The guidelines used for diamonds and colored gemstones are different. Colored gemstones have more inclusions than diamonds, are not so neat,  and there are certain gemstones that hardly ever appear clean.

MdMaya Gems uses the following clarity scale when grading gemstones.

Sometimes these inclusions are what make stones valuable (silks in rubies, the cat's eye effect in the alexandrite, etc.)

Setting aside translucent and opaque gemstones, the first classification to take into account is: 

• Type 1: Stones that are often inclusion free: Gemstones that usually don't have inclusions.  Aquamarine, morganite, heliodor, chrysoberyl – excepto alexandrite,  spodumene, blue topaz, zircon, tanzanite, …

THE FOUR FAMOUS  “C”

Color, Clarity, Cut and Carat, are the four famous  “C’s”.

We need to take into account what it is that we intend to describe with the 4 C’s: A diamond or a colored gemstone?

 

The concept of inclusion can be defined as follows:

• Inclusions are small-sized minerals located inside a larger-sized crystal (host crystal).
• Cavities that appear in the mineral, filled with liquid and/or gas.
• Such inclusions are characteristic of the hosting crystal and they are a sure way to differentiate natural gems from synthetic ones.

When I examine a gem, I always follow the same steps:

Small concepts you need to know; it is very important to know, at all times, what you are buying.

Is it wrong to buy a synthetic diamond?  NO, provided the seller says IT IS A SYNTHETIC DIAMOND. This means it will be cheaper and that both the buyer and seller are on equal terms,and the buyer won´t feel cheated. Because he/she is buying a diamond, with all its physical characteristics, albeit a man-made diamond, so its price will be noticeably cheaper.

Is it wrong to sell a treated rubythat has been filled with lead glass? NO, provided the seller specifies this information and explains that lead glass-filled rubies have a low economic value, as very often there is a higher quantity of lead glass than of ruby. Lead glass is easily damaged, so it requires special care and handling, because any damage is irreversible.If the buyer knows all of this and still decides to buy the ruby, then the transaction is completely ethical.