Lecture 15 - Diamonds

Question 1

Graphite

Answer 1

Sheets of carbon atoms arranged in hexagons and stacked

Question 2

Diamond

Answer 2

Tetrahedral framework

Question 3

Diamond

Answer 3

Tetrahedral framework

Question 4

Diamond info

Answer 4

Hardest natural structure
Annual production of 142 million carats 2019
Carat = 0.2 gram
Global reserves. - 1.2 billion carats

Question 5

Global diamond production

Answer 5

Russia, Botswana, Canada, Angola, SA

Question 6

Diamond classification

Answer 6

Diamonds produced in 21 countries.
For gems and industry
Gems = SA, Namibia, Russia
Industry = Austrailia, Congo

Question 7

How are world diamonds sold:

Answer 7

Central Selling organisation - De Beers - London based
- A Cartel to maintain high price
- Represent 80% of global trade

Question 8

Geology of Diamond occurrences and mining

Answer 8

• Mainly found in precambrian cratons in kimberlite and lamproite pipes
• open pit
• underground
• alluvial
  marine

Question 9

Kimberlite Pipe

Answer 9

• carrot shaped
• ultramafic rock
• highest grade found on crater rim
• found in thick continental crust
• Diamonds found as xenocrysts in K - rich, ultramfic rock called Kimberlite
• 1 gram diamond per 10 tons mined

Question 10

Kimberlite: intrusive igneous rock crystallized from mantle-derived magma that contains diamonds in the rock matrix

Question 11

Origins of Kimberlite

Answer 11

• from the mantle at depths >150km.
• ## Rapid ascent rate to avoid conversion to graphite.