Specialist Designer Craftsman in Jewellery :

Precious and Semi-Precious Stones

This page contains information about precious and semi-precious stones.


Definitions of Carats

I am often asked what is the difference in the use of the term carats in stones and precious metals.

When the term is used with precious stones it is a measurement of weight i.e one carat equals 0.2 grams. A one carat stone is written as 1ct. In the case of diamonds this is further divided into 100 points so a half carat stone might be described as 50 points or 0.5ct.

When the term is used with gold it is a measurement of quality. 24 carat gold is pure gold and too soft to be used effectively. Increasing proportions of other metals are added to pure gold to make it more appropriate for the intended application. 18ct gold is 18 parts pure gold and 6 parts other metals while 14ct gold has 10 parts of other metals and 9ct has 15 parts of other metals. The colour of gold can also be changed according to what metals are added.

Diamond Grading


Diamond grading is a very specialised field. The four Cs - Colour, Cut, Clarity and Carat weight form the basis for grading. Diamond grading companies produce diamond certificates to accompany the stones they have assessed. If you are buying an expensive diamond it is well worth having the security of a certificated stone. There are a number of recognised grading systems and the following is the one most used.

Diamond Cut



The cut has the greatest influence on the fire of a diamond. A round diamond has 58 facets and when well proportioned will reflect light to the best advantage.

 


brilliant round

pear

marquise

heart

oval

emerald

princess

 

Diamond Clarity



Most diamonds have minute traces of non-crystalline carbon. They are called inclusions. Perfect clarity means there are no discernible inclusions when a diamond is viewed under a 10x lens.


Flawless (FL) Shows no inclusions or blemishes under 10x magnification.

Internally Flawless (IF) Shows no inclusions and only Insignificant blemishes under 10x magnification.

Very Very Slightly (V VS) Contain minute inclusions that are difficult for an experienced grader to locate at 10x magnification.

V VS1 Inclusions are extremely difficult to see.

V VS2 Inclusions are very difficult to see.

VS1 Contain minor inclusions under 10x magnification Small crystals, feathers and clouds are typical. Inclusions are difficult to see.

VS2 Contain minor inclusions under 10x magnification Small crystals, feathers and clouds are typical. Inclusions that are somewhat difficult to see.

SI 1 Contain noticeable inclusions under 10x magnification that are easy to see.

SI 2 inclusions may bee seen without magnification.


Imperfect(I) Contain obvious inclusions under 10x magnification, which can often be seen easily face-up with the unaided eye. They may seriously affect the stones potential durability, or are so numerous they affect the stones transparency and brilliance.

I1 Beauty or durability are somewhat affected

I2 Beauty or durability are seriously affected

I3 Beauty and durability are very seriously affected

 

Diamond Colour

 

D E F
Colorless
G H I J
Near colorless
K L M
Faint yellow

d

e

f

g

h

i

j

k

l

m
N O P Q R
Very light yellow
S T U W X Y Z
Light Yellow

n

o

p

q

r

sz

 

Diamond Carat

 


0.05ct

0.10ct

0.25ct

0.50ct

0.75ct

1ct

1.25cts

1.5cts

2cts

2.5cts

3cts

4cts

The illustrations used above are used as a guide only. Lapidary is a very complex subject - you should read the excellent book "Diamonds by Noble Gems International" if you are interested in the finer points of lapiadry.

 


Email : Selwyn@selwyngale.co.uk © 2001-2015. Last Updated Sat Dec 22 13:14:40 2012 Terms & Conditions