Assignment 16 - Lab-grown Diamonds Flashcards
What technologies are used to create lab-grown diamonds?
The two major technologies are:
- high-pressure, igh-temperature, (HPHT)
- Chemical vapor disposition (CVD)
What were the early limitations of diamond growth in the lab?
- Size of equipment
- Costs
How has the marketplace for lab-grown diamonds transformed since they were first produced?
Due to high production costs, the use of lab grown diamonds was limited in jewelerey before 2000. Until 2010 mostly small and colored damonds were available.
How are diamonds grown using the HPHT method?
HPHT Diamonds are grown in conditions that replicate the earth’s natural process.
Diamonds are produces by converting a solid carbon source to diamond with a HPHT press.
Pressure: 50-60k bar
Temp: 1’300 - 1’600°C
What diamond types does the HPHT method produce?
Labgrown diamonds are typcially type Ib (nitrogen) or colorless type IIa or weak IIb (not a lot of boron). Type II is significanlty more costly to produce.
What are some identifying features of HPHT diamonds?
The only internal inclusions are remenants of the metal catalyst it grew in.
Strains in crystal lattice.
HPHT diamonds typically have a stronger fluorescence under shortwave UV than longwave UV.
Blue and colorless HPHT often show green-blue photophorescence.
A substance that increases the rate of chemical reaction
Catalyst
A crystal with both octahedaral and cubic faces
Cuboctahedral
A three-dimensional region iwth common crystallographic growth plane.
Growth sector
Spectral colors caused by the interaction of two light rays seen under crossed-polarized filters
Interference colors.
How are diamonds grown using the CVD method?
By converting a gaseous carbon source to diamond using a reactor
What diamond types does the CVD method produce?
The majority are type IIa
What are some identifying features of the CVD lab-grown diamonds?
Most CVD diamonds cannot be identified using standard gem-testing equipment and must be submitted to a lab for indentification.
How do diamond screening devices work?
most diamond screening devises work based on the fact that most natural diamonds are type Ia.
What guidelines exist for disclosures and marketing of lab-grown diamonds?
FTC-Guidelines
CIBJO-Practices
