Mdmw-diamond06

ALLUVIAL DIAMONDS S.S. Nayak

Introduction What is diamond? • Diamond is a form of carbon crystallising in cubic system. • It is the hardest naturally occurring substance on the earth. • Among the gemstones diamond reigns supreme as it is the most lasting and valuable by virtue of its exceptional physical (extreme hardness), optical (high refractive index and dispersion) and chemical (resistance to acids) properties. • Diamond is referred to as ‘King Gem’ an emblem of fearlessness. • The name diamond owes its derivation to the French word diamant.

Where do we find diamonds? Diamond occurs in economic quantities in two environments •

A special variety of rare igneous rocks known as kimberlites and lamproites, which constitute the primary host rocks on the surface of the earth

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Conglomerates and gravels which form the secondary host rocks.

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Picritic dykes, ultramafic lamprophyres, carbonatite, alkali olivine basalt, peridotites, meta-dunites and meteorites, ultra high pressure metamorphic rocks – of academic value

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The kimberlites and lamproites were emplaced during different geological times the peak of emplacement event being during the Upper Proterozoic and Cretaceous.

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Some of the oldest secondary occurrences include the Witwatersrand conglomerate (2.7 Ga) in S. Africa and Tarkwian conglomerate (2 Ga) in Ghana.

World Diamond Production (million carats) Country Angola Australia Botswana Brazil Canada Central Africa Republic China Congo Ivory Coast Ghana Guinea Liberia Namibia Russia Sierra Leone South Africa Tanzania Venezuela Zimbabwe Others Totals

India

2000 6 26.7 24.6 0.9 2 0.5

2001 5.1 23.8 25.1 1 2.6 0.48

2002 6 33.6 28.4 0.7 3.7 0.5

1.1 17.5 0.3 0.88 0.55 0.2 1.6 23.2 0.6 10.78 0.09 0.1 0.02 0.40 118

1.18 18.2 0.3 0.87 0.36 0.17 1.49 23.2 0.6 11.77 0.03 0.12 0.05 0.27 117

1.19 18.2 0.25 0.96 0.37 0.2 1.35 23 0.6 10.88 0.02 0.05 — 0.09 130

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INDIAN DIAMOND SCENARIO  Emerged as the fastest growing jewellery exporter in the world  Average growth of nearly 40% each year over the last decade  Grown from $ 28 million in 1960s to $ 9.1 billion in 2002-03  Diamond accounts for 80% of the total exports with gold jewellery contributing 16%  Established as the world’s largest manufacturing centre of cut & polished stones 60% in terms of value 85% in terms of caratage 92% in terms of pieces 11 out of 12 stones  In the last 20 years Indian trade increased from 25% to 65%

Why Alluvial Diamonds • • •

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The finest of diamonds are found in the Alluvial deposits Diamonds recovered larger in size than those recovered from the primary sources Alluvial diamond prospects, are ideally suited for local artisan exploitation because of the low capital investment required for collection and processing of the gravel. Alluvial diamonds may lead to the discovery of Primary diamond deposits

Distribution of Alluvial Diamond Deposits • Historically the alluvial diamond deposits along the Krishna and Pennar Rivers in Andhra Pradesh predate the discovery of the primary source rocks (kimberlites in 1871) by centuries • Present day economic alluvial deposits: – Zimbabwe, Angola, Zaire, Central African Republic, Tanzania, Namibia, Seira Leone in Africa – Smoke Creek and Bow River alluvial mines in northern Australia – Brazil and Venezuela in South America – Bagain River Panna area, India

AFRICA THE DIAMOND CONTINENT

AFRICA – THE DIAMOND CONTINENT

Diamond and or kimberlite or lamproite pipe areas

Distribution of cratons and archons with primary and secondary diamond deposits

FIRST DIAMOND FINDS IN AFRICA

Eureka - 10.73 ct (21.3 ct) Diamond from De Kalk farm, 1866

Area of first Diamond reports between the Orange and Vaal Rivers Erasmus Jacobs

Illicit diamond mining operations in western Africa

DIAMOND IN SOUTH AMERICA

Map showing principal Diamond regions in Brazil

Dredging and processing of river gravels in Venezuela

Angola – Source of secondary diamonds

Lucapa corridor, Angola containing diamond deposits

Potholes field with diamondiferous gravel, Angola

Famous Diamonds from the Krishna Valley

The Hope diamond

THE NIZAMS’ JEWELS

GOLKONDA FORT

DIAMOND FAME OF THE DECCAN-THE LAND OF FIRST DIAMONDS IN THE WORLD

“And you just know that diamonds are not found in any part of the world except in this kingdom (Motupalli Kingdom) alone. But here they are both plentiful and good”. Marco Polo, Venetian explorer of the 13th century “These diamonds are the first found in India in a Kingdom of Morres, named Deccan, from whence they are brought to other regions” Uertomannus, Italian Traveller (~AD 1503)

Ancient diamond mines, trade routes and European travellers

DECCAN (THE LAND OF FIRST DIAMONDS IN THE WORLD) “And you just know that diamonds are not found in any part of the world except in this kingdom (Motupalli Kingdom) alone. But here they are both plentiful and good”. Marco Polo, Venetian explorer of

13th century

Kolluru Paritala

“These diamonds are the first found in India in a Kingdom of Morres, named Deccan, from whence they are brought to other regions” Uertomannus, Italian Traveller (~ADMatanga 1503) Jonnagiri

Wajrakarur

Mallavelli

Banganapalle

Basavapur

Srikantakam (Vedaparvata)

Central and Eastern India Panna

Madhyamarastrakam/Tajjamarastrakam (Kosala country)(Vindhya Pradesh)

Sabharastrakam/Veena River (Vidharbha Region) Wairagarh

Mahanadi

Kalinga Indravankam

Indravan

Map Showing Ancient Diamond Mines

Somelpur

Paundra?

CRITERIA FOR DIAMOND CONCENTRATION • Channel morphology – alluvial diamonds concentrate in specific portions of river channels or beach deposits – Point bars, channel bars – Change in channel gradient – Pot holes, crevices, sink holes in limestone terrain • Bedrock characteristics - Lithological variations result in bedrock riffles which cause energy fluctuations along the channel • Gravel characteristics –

Rich alluvial diamonds are associated with well sorted (mature) clast supported gravels

SOUTH INDIAN DIAMOND PROVINCE

Krishna - the Diamond river from southern India Kolluru

Raichur Kurnool

Krishna River, Kolluru – Chandralapadu Area

SATELLITE IMAGERY OF ALLUVIAL DIAMOND MINING AREAS ALONG KRISHNA RIVER

River Bed Gravel, Kolluru Area

Excavation for Diamondiferous Gravel, Veladikottapalem Area

K R I S H N A R I V E R

Potholes, Krishna River Bed

Krishna Gravels

Kolluru – The Home of Historic & Famous Diamonds

d n o m a s, i D ing rea t n rk A e i c o ru n A Wollu K

Ancient Workings, Kolluru Area

PARITALA MINE KRISHNA RIVER GRAVELS

Processed Dumps, Kolluru Area

Washing Tank, Mallavaram Area

Processed Dumps

T3 Gravels, Ustapalle – Kolluru Area

ANCIENT TOMBS, KOLLURU AREA

MENHEIR – AN ANCIENT TOMB KOLLURU AREA

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g n i s es

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v a Gr

P l e

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Penner River Gravels

Gravel overlying the Owk Shale, Jammalamadugu Area

Processed Dumps, Chennuru Area

Sagileru River Gravels

DIAMONDS FROM ANDHRA PRADESH

PANNA DIAMOND BELT The Panna Diamond Belt encompasses an area of 1000 sq km. And extends from near Majhgawan in the west to Jhanda in the east over a strike length of about 60 km and width of about 30 km Source Rocks: Primary:

Kimberlite (Lamproite) at Majhgawan

Secondary: A. Conglomerates: Itwa Conglomerate Jhiri Conglomerate Gahadra Conglomerate B. Alluvial C. Lateritic gravel

DIAMONDIFEROUS GRAVELS, BAGAIN RIVER, PANNA AREA

PRESENT DAY ALLUVIAL DIAMOND WORKINGS, BAGAIN RIVER, PANNA AREA