General

The diamond is regarded king of gemstones although it is not the rarest gem mineral. There are gemstones which are much more rarer.
Because of its hardness diamonds can be cutted only with diamond powder. Diamond is durable to most chemicals except sulfochromic acid. There are different types of diamonds which differ in absorption spectrum, fluorescence, electrical conductivity, and cleavage. That has to be considered while cutting.

Formation and Resources

Very deep in the earth's mantle, under high pressure and 1,100-1,300°C, diamonds developed from carbon. They were transported to the surface by vulcanic eruptions.
The todays most important resources are in South Africa (primary resources), Namibia (secondary resources), and Russia (primary resources). In South Africa and Russia one had to dig deeper and deeper while in Namibia one can mine the diamonds in opencast mining by use of dredges. The resources in Brazil and other countries are comparatively unimportant. The South African diamonds mining industry has created the "Big Hole", an open-pit mine in Kimberley, the largest or second largest excavated hole worldwide (240 m deep, 463 m wide). 1914 the opencast mining stopped, and water filled the hole partially. Since then the underground Kimberly Mine was mined to a depth of 1,097 m. Approximately 15 million ct of diamonds have been mined there.

International Diamond Grading

80% of all diamonds are used for technical purposes (e.g. drill bits). The rest (20% better stones) is assessed according to the "4 C's": 1. Color, 2. Clarity, 3. Cut, 4. Carat weight.

1. Color:

Most of the diamonds are yellowish which causes lower prices, in contrary to other colors. Today special instruments are increasingly used for the color analysis because the human eye cannot neutrally distinguish between the fine color nuances.
The established diamond colors range from D to Z (GIA / Gemological Institute of America).
A different system is the Scandinavian Diamond Nomenclature:
D, E: "Colorless", "River"
F: "Colorless", "Top Wesselton"
G: "Near Colorless", "Top Wesselton"
H: "Near Colorless", "Wesselton"
I: "Near Colorless", "Top Crystal"
J: "Near Colorless", "Crystal"
K - L: "Faint Yellow", "Top Cape"
M: "Faint Yellow", "Cape"
N: "Very Light Yellow", "Cape"
O - R: "Very Light Yellow", "Light Yellow"
S - Z: "Light Yellow", "Yellow"
"Fancy" - strong colored (orange, rose, red, green, blue), and very sought by connoisseurs.

2. Clarity:

Measure for the amount of inclusions in diamonds (10x loupe). Clarity grading scale (GIA):
FL ("flawless") = Loupe clean , free from inclusions.
IF ("internally flawless") = Loupe clean, free from inclusions.
VVS1 ("very, very slightly included") = Very hard to find with a 10x loupe.
VVS2 ("very, very slightly included") = Very hard to find with a 10x loupe.
VS1 ("very slightly included") = Very small inclusion(s), which can hardly be found with a 10x loupe.
VS2 ("very slightly included") = Very small inclusion(s), which can hardly be found with a 10x loupe.
SI1 ("slightly included") = Small inclusion(s), easy to find with a 10x loupe. Not visible with the naked eye through the crown side.
SI2 ("slightly included") = Small inclusion(s), easy to find with a 10x loupe. Not visible with the naked eye through the crown side.
I1 ("imperfect") = Inclusion(s) immediately evident with a 10x loupe. Difficult to find with the naked eye through the crown side, not impairing the brilliance. Also known as "P1".
I2 ("imperfect") = Large and/or numerous inclusion(s), easily visible to the naked eye through the crown side, and which slightly reduce(s) the brilliance. Also known as "P2".
I3 ("imperfect") = Large and/or numerous inclusion(s), very easily visible to the naked eye through the crown side, and which reduce(s) the brilliance. Also known as "P3".

3. Cut:

Grading scale (GIA): "excellent", "very good", "good", "fair", "poor".

4. Weight:

(ct / Diameter):
0.10 ct = 3.0 mm
0.25 ct = 4.1 mm
0.50 ct = 5.2 mm
1.00 ct = 6.5 mm
2.00 ct = 8.2 mm

Prices: see e.g. Diamondse.info - the diamond search engine

Relation between weight and price: see Graph

⇐ Intro Page ⇐ Gemstones ⇐ Diamond