Diamonds- An introduction

1. DIAMONDS
BY: KUNAL SULEKH

2. The term Diamond has been derived from the
Greek "adamas"--unconquerable.
Long known for hardest of naturally
occurring minerals, index 10 on Mohs scale of
hardness.
These are known to be among the oldest
minerals in the earth. (Richardson el al., 1984)
These are still weighed in the old unit known as
carats.
DIAMOND

3. Diamonds are found in Australia, Botswana,
Canada, Namibia, Russia, South Africa,
Venezuela, Brazil, India, China, Indonesia, D.R.,
Congo, Guyana, Ghana, Ivory coast, Liberia,
Tanzania and Zimbabwe.
Generally, these are found in stable part of
Earth's crust.
DIAMOND

4. Primary and Secondary
Primary sources are the kimberlite and
lamproite pipes that raise diamonds from
Earth's mantle, where they originate.
Secondary sources, created by erosion, include
such deposits as surface scatterings around a
pipe, For eg.: concentrations in river channels.
Total world production of natural diamonds is
about 97 Mct p.a.
TYPES OF DIAMOND DEPOSITS

5. India was the only source of diamond until
1725.
In 1725, Brazil diamond deposits (Minas Gerais
and Bahia) were discovered and were used for
about 150 years.
At present, Australia has been the major
diamond deposit since 1986 (1/3 world
production annually).
DIAMOND DEPOSITS

7. Kimberlite has traditionally been considered to
be the only important primary source of
diamond. (Scott Smith & Skinner, 1984)
Kimberlite may be defined as a potassic
ultrabasic hybrid igneous rock containing large
crsytals (megacrysts) of olivine, enstatite,
diopside in a fine-grained matrix.
Lamproites are defined as potash- and
magnesia-rich lamprophyric rocks of volcanic or
hypabyssal origin containing clinopyroxene,
amphibole, leucite and sanidine.
KIMBERLITE AND LAMPROITES

8. Lamproites have greater mineralogical and
textural variations than Kimberlites.
Lamproites craton are generally wider and
shallower than those of Kimberlites.
There are 2 period of diamond formation.
First about 3.3 Ga (Peridotitic minerals)
Second about 1580-990 Ma ago. (Eclogitic
minerals)
KIMBERLITES AND LAMPROITES

10. DIAMOND DEPOSITS

11. Diamonds were discovered in India by the 4th
century BCE. India yielded many legendary
diamonds, including the Koh-i-Noor, the Orlov,
the Hope, and the Sancy.
The history of the stone which was eventually
named the Hope diamond was most likely from
the Kollur mine in Golconda, India. Its color was
described as a "beautiful violet."
India was the world's only source until the
1730s. Most of India's deposits were alluvial, but
today the Majhgawan pipe, a primary source
near Panna, is the country's only producing
diamond source.
INDIA

12. These are the 4 different ways by which
diamonds are evaluated
Cut
Color
Clarity (inclusions)
Carat Weight
THE 4 C'S

14. THANK YOU