Transcript diamond - Geological Sciences, CMU

Diamond
Diamonds are found in Australia, Botswana,
Canada, Namibia, Russia, Sierra Leone, South
Africa, Brazil, Venezuela, China, India,
Indonesia, the Central African Republic, D.R.
Congo, Guyana, Ghana, Guinea, the Ivory
Coast, Liberia, Tanzania, and Zimbabwe.
Only 20% of the diamonds mined are suitable for
polishing, and about 80% are industrial qualities
which are used in the medical field, in the space
programs, and for industrial diamond tools amongst
o t h e r
t h i n g s.
Types of Diamond Deposits
Geologic processes create two basic types of
diamond deposits, referred to as primary and
secondary sources. 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, concentrations in
river channels, and fluxes from rivers moved
by wave action along ocean coasts, past and
present. Mining of these deposits depends
upon sufficient concentration and quality of
d i a m o n d s.
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.
In 1866, diamonds were discovered in the gravels of the Vaal River, South
Africa..
The United States has produced a few diamonds .The well-known U.S. diamond
deposit is at Crater of Diamonds State Park in Murfreesboro, Arkansas. The
largest U.S. diamond, the "Uncle Sam" which weighs 40.23ct, came from this site.
In late 1991, of a diamond-bearing kimberlite of apparent economic potential at
Point Lake, near Lac de Gras in the Northwest Territories,
At present, Argyle diamond deposits (discovered in 1979), W.Australia has been
the major diamond deposit since 1986 (1/3 world production annually).
Distribution of World Diamond Deposits
GEOLOGY OF DIAMOND DEPOSITS
Occurrences
Where : cratonic areas
Assoc. rocks : Kimberlites or
Lamproites
Diamond deposits
Primary : in diamond pipes
Secondary: in sediments
Schematic model of a fully grown kimberlite pipe
Diamond mining
Onshore : surface/underground
Offshore: sea bed
Formation of a diamond pipe
Inclusions as indicator of the origin of diamonds
(a.)
(b.)
a.) A purple pyrope garnet, an indicator of
garnet harzbugite , Udachnaya pipe, Russia.
b.) Orange garnet, typical of diamond eclogite.
c.) Red Cr pyrope and green Cr diopside
indicators of a peridotite, Mir pipe, Russia.
(c.)
PROCESSING DIAMOND ORE
Cones and cyclones use swirling
heavy fluids mixed with crushed
ore to achieve density
separations.
With 99 percent of the waste in
the ore removed, further
separations may use either a
grease table or an x-ray
separator.
Final separation and sorting is
done by eye.
The x-ray separator system acts on a thin stream of particles from the concentrate
accelerated off a moving belt into the air, where they encounter an intense beam of x-rays.
Any diamond fluoresces in the x-rays, activating a photomultiplier that triggers a jet of air,
deflecting the diamonds (blue) into a collector bin. Adapted from Bruton (1978).
PRINCIPAL DIAMOND PRODUCERS
Africa
• South Africa
• Namibia
• Botswana
North America
• Canada
• USA
Australia
• Western Australia
Eurasia
• Russia
• India
• Southeast Asia
Diamond Mining is undergoing a resurgence with several African
Mining Companies operating major mines. De Beers in South Africa;
Debswana in Botswana, Miba in the Congo and Namdeb in Namibia
are the major African Producers. A large number of diamonds are being
hand mined by locals and sold to buyers. In Australia, Ashton Mining
are continuing with AK1 pipe in the Kimberley as an open cut
operation and are opening new diamond mines at Cempaka in
Kalimantan, Indonesia and Merlin in NT, Australia. The Cempaka
alluvial deposits are mined with dredges. Merlin is open cut with
several diamondiferous kimberlite pipes. BHP is continuing mining the
E k a t i D e p o s i t i n C a n a d a.
(
http://www.geologynet.com/miningnews.htm)
*Table I: Estimated 1999 Diamond Production by Country
Country
Botswana
Carats (‘000) Value ($ m)
21,348
1,612
Russia
16,200
1,523
South Africa
9,733
D.R. Congo
Country
Carats (‘000) Value ($
m)Venezuela
450
58
Brazil
900
41
985
Tanzania
232
37
22,000
725
Liberia
200
32
Angola
3,625
544
Ivory Coast
165
24
Australia
29,784
437
Ghana
500
19
Canada
2,510
422
China
146
15
Namibia
1,611
413
Lesotho
43
15
Sierra Leone
600
138
Guyana
11
1
Guinea
550
120
Total
Central Africa Rep
450
92
7,253
111,058
*Source: Mining Journal, Londo
AFRICA
Africa is the richest continent for diamond mining, accounting
for roughly 49% of world production. The major sources are
in the south with lesser concentrations in the west-central part
of the continent. The major producing countries are Congo
Republic (Zaire), Botswana, South Africa, Angola, Namibia,
Ghana, Central African Republic, Guinea, Sierra Leone, and
Zimbabwe. Political turmoil in some countries has led to highly
variable production and severe degradation of the environment
from uncontrolled mining.
Primary Deposits
D.R. Congo (19.81%), Botswana (19.22%), South Africa (8.76%), and Angola(3.26% )
Secondary Deposits
Onshore : Angola and South Africa
Offshore : South Africa and Namibia (1.45%)
Other African producers and their percentage of world
production in 1999
Central African Republic 0.40%
Ghana 0.45%
Guinea 0.50%
Ivory Coast 0.15%
Lesotho 0.04%
Sierra Leone 0.54%
Tanzania 0.21%
Source: Mining Jour., June 16, 2000
Diamond Deposits of Orange River Valley
Diamonds have been transported
across the vast area of southern
Africa shown on this map. There are
more than 3,000 kimberlite pipes -many not bearing diamonds, of
course -- in the craton drained by
tributaries to the Orange River and its
precursors, which end at the Atlantic
coast. The rivers carried water,
sediments, and diamonds to the
o
c
e
a
n.
Alluvial mining of diamond deposits.
SOUTH AFRICA
South African Production
Total: 520 million carats
Annual 1870: 269,000 carats
1903: 3 million carats
Today: 8 to 10 million carats
9.73 million carats in 1999
•Onshore and offshore deposits
•De Beerss and Southern Era Co.
http://www.geotoursafrica.com/english/geology.htm
http://www.webace.com.au/~kati/africa.html
Could be a scene from the cold war, but its actually the
security fenceline to a South African diamond mine.
The Venetia diamond mine,
w h i c h o p e n e d i n 1992,
represents one of De Beers’
largest single investments in
South Africa. Situated 80 km
from Messina in the Northern
Province, and involving an
investment of R1.1 billion
(US$400 million) the mine is
South Africa’s largest
diamond producer, with an
output of 4.3 Mct from 3.4 Mt
of ore in 1997, and 4.5 Mct in
1998. It employs about 700
p
e
o
p
l
e.
http://www.mining-technology.com/projects/de_beers/
Scenes from Venetia Mine
http://www.webace.com.au/~kati/africa.html
Can't quite understand the meaning of this sign at the
Venetia diamond mine but it seems funny anyway!
http://www.webace.com.au/~kati/africa.html
A bank of four x-ray machines sorts the precious diamond
from waste material
Kimberley Mine in 1873
From "The Diamond Mines of South Africa,"
G.F. Williams, New York, 1906.
Barney Barnato
Cecil John Rhodes
Kimberley Mine, the Big Hole on Earth, today.
Premier Mine, home of the 3106 carat Cullinan diamond.
A cross section of the underground workings at the Dutoitspan mine,
Kimberley, South Africa. Adapted from De Beers
NAMIBIA
• Part of an extremely old region, with > 2.0 Ga. basement rocks.
• The basement rocks are usually covered by Mesozoic sediments.
• Tectonic activity over the last 100 Ma. or so created a number of
rifts and the uplifting of most of the area above sea level.
Onshore mining in Namibia has produced 70 million carats
since the first diamond rush in 1908.
Namibia’s diamonds derive not from primary kimberlite pipes,
but from secondary diamond deposits areas where diamonds
have been washed down and deposited by old rivers, which
have eroded kimberlite pipes in the interior on their way.
Namibia
In the early days, from 1908 to 1910,
diamonds were recovered from the
coastal sands in Namibia by
workerscrawling on hands and knees.
In 1908 a railroad worker found diamonds in the sand dunes near
K
o
l
m
a
n
s
k
o
p
,
South West Africa (now Namibia), then a German colony. In 1909 almost
500,000 carats were produced there, and yields almost tripled in 5 years.
The diamonds were small but of high quality. South Africa gained control of
Namibia after World War I and sold the diamond deposits to Consolidated
Diamond Mines (CDM), which was transferred to De Beers in 1929. In
1994 CDM was reconstituted as Namdeb Diamond Corporation Limited and is
now jointly owned by the Namibian government and De Beers. The production,
• A Texan named Sammy Collins drew worldwide attention in 1962
announced the discovery of 50,000 carats of diamonds worth $1.5
million from the seabed of the Diamond Coast of South West Africa.
The diamonds were carried there by the Vaal and Orange rivers
from some far inland deposit, they also ought to be found under the
ocean.
• Over a period of three years, Collins used the equivalent of huge
vacuum sweepers to suck some 400,000 carats of diamonds from
the seabed.
• Today, with improved technology, De Beers and others are once
again probing the waters of the South Atlantic, bringing closer the
prospect of viable undersea diamond recovery in the 1990's.
Suction pipes used to pump diamond-bearing
gravel are being moved into the surf by divers
at DePunt, South Africa.
There are 3 types of marine
mining operations. In one,
s a n d is mo v e d fro m 10
meters below sea level to as
far inland as the sea may
have risen, in order to reveal
the concentrations on the
bedrock. In another, divers
and boats work in the surf
zone to perhaps 20 meters
of water and use suction
pipes to remove gravel and
diamonds from the ocean
floor. In the third, deep-sea
marine vessels use remote
The mining vessel "Geomaster" of the De
Beers Marine fleet working off the coasts of
Namibia and Namaqualand, South Africa. It is
capable of operating in depths up to 200 m
(660
f
e
e
t
).
Because powerful ocean waves break
the poorer quality diamonds, 90-95
percent of marine diamonds are of gem
quality. The littoral zone, the area of
wave action on the Atlantic coast where
diamonds accumulate, has moved in
and out with changes in sea level, but
shore lines have been constant over
long periods, resulting in wave-cut
terraces with hollows and crevices in
which diamonds concentrated. These
terraces are preserved hundreds of
meters both above and below sea level
and are the focus of mining activity.
Massive sand walls keep back the sea
during mining of diamond-bearing terraces
in the foreshore. Consolidated Diamond
Mines (now Namdeb) has successfully
employed this engineering technique in
Namibia.
After removal of many meters of Kalahari
sands from the bedrock surface on
Namibia's west coast, workers scour
exposed crevices and crannies for
diamonds.
BOTSWANA
Botswana's mining minister K. Moshashane, said that diamonds
(70% of his country's earnings)"have transformed Botswana from
dire poverty into a stable democratic developing country.”
Nicky Oppenheimer, the Chairman of De Beers Consolidated
Mines Ltd., stated, "Since the discovery of its diamond deposits,
Botswana has achieved record economic growth."
Ref. http://www.keyguide.net/rough/
De Beers discovered 3 world-class kimberlite
deposits in Botswana between 1967 and
1973. The Orapa pipe, found in 1967,
is the second largest economic kimberlite pipe
in the world and produces about 5.5 million
carats annually. The Jwaneng pipe was
discovered in 1973 under the sands of the
Kalahari Desert. With over 10 million carats
produced in 1995, it was the second most
productive mine for weight of diamonds but
first for currency value. Two smaller pipes,
Letlhakane 1 and 2, were discovered in
1968. Botswana's diamond reserves are
The Orapa Mine has been in production since
biggest
in
i 1971
m and mis the second
e
n
smine e.
Botswana, currently producing more than 6 million carats per annum, worth over $400
million. An expansion to the mine, due for completion in 2000, will double capacity to
The Jwaneng mine, in Botswana, is the most valuable diamond mine in
the world. Its 1995 production of about 10.5 million carats had a value
of about $1.2 billion.
Congo Republic (Zaire)
W i t h 19.8% o f
world production,
this is the second
largest producer of
diamonds by
weight (22 million
c a r a t s i n 1999)
after Australia. Only
6% is of high gem
quality; another
40% c o n s i s t s o f
small stones, called
AUSTRALIA
• W.Australia , New South Wales,
Queensland
• Kimberley regions (Ellendale
and Argyle areas)
• Argyle AK-1 and Bow River
deposits are most productive
• 29.7 million carats in 1999
Argyle diamond mine, Western Australia and its diamonds.
In 1979, a large lamproite pipe was found and named the Argyle mine; by
1992 over 200 million carats had been mined there. Only 5% of the
production is gem quality. A unique feature of the Argyle mine, though, is a small
but consistent supply of valuable pink to red or purple diamonds.
Argyle Diamond Pipe
The Argyle diamond pipe is in a
small valley at the southend of
the Matsu Range. The pipe is
about 2 km long by 150-500 m
wide and steep-sided. The shape
of the pipe has been modified by
faulting. In this photo, the dirt
road runs on the pipe along the
valley floor.
The most common rocks are quartz-rich
lapilli ash tuffs
Cross-section of the Argyle diatreme
from Boxer and others (1989).
Intrusive olivine lamproite dikes and
fine-grained quartz-rich sediments
Most of the diamonds at Argyle are
resorbed dodecahedron.
A small percent of the diamonds
from Argyle are sharp-edged
octahedra with hexagonal surface
pits.
Diamond deposits of North America
UNITED STATES OF AMERICA
Near Murfreesboro, Arkansas, from what is now
known to be a lamproite pipe, more than
100,000 stones averaging 0.25 carat each were
produced between 1907 and 1933. Now Crater of
Diamonds State Park, the locality is a stop
for hobbyists and tourists. The "State Line
Kimberlite District" along the ColoradoWyoming border is home to the only operating
diamond mine in the U.S., started at Kelsey
Lake, Colorado, in June 1996. The largest
diamond found so far is 28.3 carats, and
a b o u t 25% o f t h e 20,000- c a r a t a n n u a l
p r o d u c t i o n i s o f g e m q u a l i t y.
KELSEY LAKE DIAMOND PIPE, COLORADO
Excavation of the Kelsey Lake #1 kimberlite, which began mining in June, 1996.
Crater Of Diamonds State Park
AUSTRALIA
Arkansas, USA
• Southwest Arkansas near Murfreesboro is a rare 35-acre field where
diamonds
can be
found
in
their
natural
m a t r i x.
• The only diiamond area in North America open to the public.
• Over 70,000 diamonds found at the "Crater" (an eroded volcanic pipe).
• The big finds are the Uncle Sam (40.23 carats), Star of Murfreesboro
(34.25 carats), Star of Arkansas (15.33 carats), and the Ama-rillo Starlight
(16.37
c
a
r
a
t
s
).
• An average of more than 600 diamonds are found each year.
• Amethyst, agate, jasper, quartz, calcite, barite and many others,
including over 40 different rocks and minerals, make the area
a
r
o
c
k
-
h
o
u
n
d
'
s
d
e
l
i
g
h
t.
Anyone can search for diamonds at
the Crater of Diamonds State Park,
M u r f r e e s b o r o , A r k a n s a s.
17 carat Arkansas diamond
crystal from Pike County from
the Roebling collection in the
US National Museum
( S m i t h s o n i a n ).
CANADA
The first kimberlite pipe discovered in the
Northwest Territories is under Point Lake. The
top of the kimberlite lies about 50 m below
the surface of the lake, which is 600 m
w
i
d
e.
Intermittent exploration
for kimberlites by major
companies was
unsuccessful through the
1980s. But Chuck Fipke,
head of Dia Met
Minerals, persevered
and in April 1990 located
a kimberlite under Point
Lake. Eventually, his
company, with partner
BHP Minerals, found
m o r e t h a n 100
By 1985, after collecting diamondindicating soil samples for nearly a decade,
Canadian geologist Charles Fipke had
followed a trail of kimberlitic minerals (those
left on the earth's surface in the aftermath of
kimberlite volcanoes) to the Lac de Gras
region of the Northwest Territories. Six years
later, with the help of an enthusiastic new
partner, BHP Minerals, Fipke and his crew
discovered the area's first ancient kimberlite
volcano or "pipe" under Point Lake. In the fall
of 1991, they recovered 81 diamonds
from a 58 kilogram core sample and
triggered the largest staking rush in Canadian
m i n i n g
h i s t o r y.
EKATI MINE
BHP Diamond Inc. and DiaMet joint venture
http://www.diamet.com/ekati_diamond.html
• A total of 121 kimberlite "pipes" have been
discovered in the Ekati™ claim area.
INDIA
The only source of diamonds until 1725
Total production : 21 million carats
Maximum annual: 50,000 to 100,000 carats in
late 1600s
Today: 20,000 carats
Diamonds were discovered in India by the 4th
century BCE. In addition to the diamond
legends, India yielded many legendary diamonds,
including the Koh-i-Noor, the Orlov, the Hope,
and the Sancy. Except for a minor supply of
diamonds from the Kalamantian deposits of
Borneo, dating from the 6th century CE, 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.
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 by Tavernier
a s a " b e a u t i f u l v i o l e t."
Golconda is often cited as a mine source
for Indian diamonds, but this ancient
capital city was a trading center; the
K o l l u r d e p o s i t s a r e n e a r b y.
Workers remove diamond-bearing gravel
under the watchful eye of an overseer in
diamond mines near Panna.
Valentine Ball. "A manual of the geology of
India." Calcutta: 1879-1887.
Diamond Washing in The Raolconda Mines.
A historic representation of diamond mining
in India, printed in 1859.
The five major historical diamond producing
regions of India are shown here. These were
mostly alluvial deposits in river channels.
Only the Majhgawan lamproite pipe, near
P a n n a , i s n o w i n o p e r a t i o n.
http://www.amnh.org/exhibitions/diamonds/india2.html
RUSSIA
• In the 1930s, academician Vladimir S. Sobolev recognized similarities between the ancient
b e d r o c k o f S i b e r i a a n d t h a t o f S o u t h A f r i c a a n d B o t s w a n a.
• In 1947, prospecting started by looking in streambeds for trails of indicator minerals.
• In 1954 in Sakha (formerly Yakutia), the first kimberlite pipe, Zarnista (Dawn) was found in the
D
a
l
d
y
n
f
i
e
l
d.
• n 1955, the very rich Mir (Peace) and Udachnaya (Lucky) pipes were discovered .
• B y 1956, m o r e t h a n 500 k i m b e r l i t e s h a d b e e n d i s c o v e r e d.
• B y 1970 R u s s i a h a d b e c o m e t h e t h i r d l a r g e s t p r o d u c e r.
• Its production is about one quarter gem diamonds, worth $1.2 billion, second to Botswana.
The Yakutia Craton in eastern Siberia is the
world's second most productive craton. Only
the Anabar Shield and Aldan Shield portions
are exposed; the rest is covered with
sedimentary rocks into which the kimberlite
p i p e s h a v e i n t r u d e d.
The main producing kimberlite areas are the Daldyn and Alakit fields (A) and the Malaya
Botuobiya field (B). Important pipes that are producing or may produce are named.
The Internationalnaya mine, only 40 km from the Mir (Peace)
pipe, has terminated above ground operations, and underground
operations have been hampered by waters that emit toxic gases.
The Mir mine in the Malaya Botuobiya field was the first
Russian mine opened in 1957. Annual production has
averaged about 2 million carats. Although the pipe has been
mined out, stockpiles and tailings (waste) continue to be worked
f
o
r
Blasting to dislodge hard kimberlite at the Udachnaya mine, the
most productive one in the Sakha Republic.
The open pit at the Udachnaya
(Lucky) pipe in Sakha
Republic, Russia, has produced
many millions of carats of
diamond. The bench steps are
a b o u t 20 m h i g h.
Inclusions of garnet and sulphides in octahedral
diamond from the Udachnaya pipe
The group of sulphides in octahedral diamond
http://space.tin.it/scienza/stalnik/mywork.htm
http://www.archangeldiamond.com/
General
Location Map
Western
Europe, NW
Russia
Russian Production
Total: 332 million carats
Annual in 1970: 7.5 mil. carats
Today: 10-12.5 million carats
Grib Diamond Pipe
Artist's Three Dimensional View
Looking Southwest
BRAZIL & VENEZUELLA
When diamonds were discovered by alluvial gold
miners in Brazil in 1725, Indian diamond sources were
near exhaustion and European demand for the stone
continued unabated. From 1730 to 1870 Brazil was
the world's major source of diamonds. Indeed, mining
in Brazil was so active that by the late 1730s
production far exceeded demand, and diamond prices
fell by as much as 70%. Beginning in 1850, production
rose again, following the discovery of rich deposits in
Bahia, but after 1861 it rapidly declined as deposits
were depleted, leading to a great shortage of rough
diamonds in the European cutting centers in the late
1860s.
Diamond mining in Brazil
Productive Brazilian
diamond deposits are
all secondary. They are
usually small, and some
are of low grade, so
mines typically operate
for short periods.
Primary diamond pipes
exist but are generally
uneconomic, suggesting
that erosion has
stripped away the
richest portions from
t h e m . I n 1890 a n d
1901, s e c o n d a r y
"A view of the manner in which the bed of the
river is laid dry by an aqueduct." From John
Mawe, "Travels in the interior of Brazil."
L o n d o n:
1812.
"View of Negroes washing diamonds at
Mandango." From John Mawe, "Travels in
the interior of Brazil." London: 1812.
Diamond deposits are widely
distributed in Brazil. Those in the
states of Minas Gerais, Bahia, Mato
Grosso, and Rora’ma have been the
most important. The shaded areas
a r e d i a m o n d d e p o s i t s.
Brazilian Production
Total: 55 million carats
Old annual: 50,000 to 300,000
carats; 1730s to 1861
Today: 1.5 million carats
SOUTHEAST ASIA
Myanmar : Momeik, Theindaw and Taungoo-Htantabin areas
Thailand: Phuket-Takua Pa area
Indonesia : Sumatra and Kalimantan areas
• Griffin,W.L., Win,T.T.,Davies, R., Wathanakul, P., Andrew, A., and Metcalfe, I,
1998. Diamonds from Myanmar and Thailand: characteristics and possible
origin (http://www.es.mq.edu.au/GEMOC/Abstrfull98/Griffin982.htm)
• Spencer, L. K., Dikinis, S. D., Keller, P. C., and Kane, R. E. (1988). "The
diamond deposits of Kalimantan, Borneo". Gems & Gemology 24: 67-80.
Distribution of alluvial
diamonds in SE Asia.
Sibumasu terrane outlined
by thick dashed line.
Inset: Permian plate
reconstruction, showing
location of Sibumasu (S)
and Western Burma (WB)
terranes adjacent to NW
A u s t r a l i a.
Carbon-isotopic composition of diamonds from Myanmar and Thailand,
compared to diamonds from Argyle and eastern Australia. .
The Southeast Kalimantan diamond fields are emerging as having potential to
host large, long life alluvial diamond deposits. Indomin’s diamond projects in
South Kalimantan are at an advanced stage with bulk testing programs
underway in both the onshore Martapura project (Indomin 60%) and the
shallow offshore Sunda Shelf project (Indomin 21% financed to production
and Trans Hex International 30% and operator). Adjoining the Martapura
project, Ashton Mining of Australia has commissioned the construction of a
dredge for diamond production from their Cempaka-Danau Seran diamond
project. The bulk testing programs underway at Indomin’s Martapura project
will determine the grade of diamondiferous gravels already outlined. If an
economic grade is defined the project will then move to a feasibility study for
diamond mining which, if positive, would make the project a potential company
m
a
k
e
r.
http://www.battlefield.ca/news/970331.htm ( October 2000)
It looks like muddy,
unpleasant work and
it may well be but the
rewards are
diamonds and a
chance for wealth.
Work in these fields,
at Cempaka in
Kalimantan, is
handed down from
generation to
g e n e r a t i o n.