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Diamonds Diamonds J.D. Price Images and much of the information - - PowerPoint PPT Presentation
Diamonds Diamonds J.D. Price Images and much of the information - - PowerPoint PPT Presentation
Diamonds Diamonds J.D. Price Images and much of the information here is from the American Museum of Natural History Diamond Exhibit, by Dr. George Harlow http://www.amnh.org Form Habit a common natural growth geometry Trigons the
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Habit – a common natural growth geometry Trigons – the building blocks of a diamond
Form
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Image from Pauling, 1970
Diamond Graphite Q: What element is represented by each sphere?
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Graphite - steep changes in energy for changes in pressure (dG/dP) Diamond - higher G at low pressure, but shallow dG/dP
G is energy
The carbon system
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At P = 5 kbar
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Carbon phase diagram
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Diamond origins
Examples of likely depths and origins for South African diamond deposits. Diamonds are formed in regions of the mantle at sufficiently high pressure. Diamonds may originate from even deeper sources in the mantle
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This volcanic structure is a diatreme The only locality to let you dig for your own diamonds: Crater of Diamonds State Park, Arkansas
Diatreme
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White dwarf BPM 3793 0.6 size of the earth White dwarves are burned-out sun- sized stars Core is carbon, formed as the end product of fusion Metalfe et al, 2004 concluded from astroseismic measurements that it is 90% solid (5 E 29 kg or 1 E 34 Carats)
Diamonds in space
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Diamonds were first discovered in India around 500 B.C. These were first weighed relative to the weight of a seed from the seed pod of the carob tree.
1 ct = 200 mg
Carat
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Archon – 3.7 to 2.5 Ga, Proton – 2.5 -0.5 Ga, Tecton - younger
Diamondiferous material hosts
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Modern diamond production
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- 1. Cullinan - 3,106.75 carats - 1905, South Africa
- 2. Excelsior - 995.20ct. - 1893, South Africa
- 3. Star of Sierra Leone - 968.80ct. - 1972, Sierra Leone
- 4. Zale - 890.00ct. - 1984, Africa
- 5. Great Mogul - 787.50ct. - 1650, India
- 6. Woyie River - 770.00ct. - 1945, Sierra Leone
- 7. Presidente Vargas - 726.60ct. - 1938, Brazil
- 8. Jonker - 726.00ct. - 1934, South Africa
- 9. Reitz - 650.80ct. - 1895, South Africa
10.Unnamed - 620.14ct. - 1984, South Africa
3K carats = 600 g = 1.3 lbs
Largest Uncut Stones
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The big hole, Kimberly, SA Mirny, Siberia d=525m Ekati, NWT
Mining
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Separating
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Abrasion (stone cutting, polishing) Jewelry Experimentation
Uses for diamond
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Gem stones are valued by four basic criteria 1.Color 2.Cut 3.Clarity 4.Carat weight
If you ever decide to seriously buy a gem stone – get a 10x or better hand lens! #1 rule: in most cases you get what you pay for.
4C’s
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Color is an important factor in the purchase
- f a diamond and can affect the price by 2-
10% per letter*
Color
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Colored stones are not popular in the US, but are heavily marketed in South America and Europe
“Fancy diamonds”
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Cut refers to shape, but its not necessarily the style that influences diamond cost
Cut
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Cutting
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Cut is so important to the value of a diamond that it can affect the value by 25% to over 50%.
Cut: the behavior of light
A missed cut sends makes light reflect, and diamond loses brilliance A perfect cut sends makes light refract to the table, and diamond gains brilliance
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Clarity is a rarity factor that affects diamond value by 5 - 20% for each increment on the AGS diamond grading scale. In most diamonds purchased by consumers, the diamond has few to no features noticeable to the unaided eye.
Clarity
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In the early 1900's the Metric Carat was established. 1 Carat = 0.2 gram
- Full Carat: A diamond that weighs or rounds to 1.00 Carat.
- Light Carat: A diamond that weighs slightly less than 1.00 Carat.
Example .96 - .00. This IS NOT a full Carat. Diamonds in this range are priced less.
- Magic Sizes: Diamonds that weigh-in exactly at or greater than a
major size category. Each major size category marks a greater degree of rarity, and commands a higher price. Q: which of the four c’s are nature’s doing, and which are the gemologist’s doing?
Carat
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Today industrial (small unclear) diamonds are readily synthesized – gem quality is a little more difficult An early GE diamond making press
Synthesis
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Gemisis Lifegem Apollo Diamondview Spectrometer (tool to separate out synthetics) Adia Not pictured Tairus - Russian NAS and Thai venture
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Moissanite SiC
Similar refractive properties Very hard (but not as hard as diamond) Absorbs more UV radiation Not combustible Q: Why the similar structure for diamond and moissanite (hint: look at the periodic table)?
Substitutes
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