Ass #16-Lab Grown Diamonds

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Questions and Answers

What is one common indication that a trained gemologist looks for when examining a CVD lab-grown diamond?

Black graphitic inclusions (correct)

Presence of bubbles in the diamond

Presence of color zoning

High levels of fluorescence under UV

Which of the following represents a distinguishing feature of CVD lab-grown diamonds compared to HPHT diamonds?

More consistent color saturation

Presence of pronounced radial fractures

Higher levels of fluorescence

Irregular or mottled strain patterns (correct)

How do HPHT-treated CVD diamonds typically fluoresce under shortwave UV light?

They fluoresce bright blue.

They fluoresce very weak to moderate green. (correct)

They fluoresce bright red.

They show no fluorescence.

What is a primary advantage of using a microscope during the examination of diamonds?

To identify growth interruptions. Signup and view all the answers

What change did the FTC implement in August 2018 regarding the diamond industry?

Amendments to the Guides for the Jewelry Industry. Signup and view all the answers

During the process of distinguishing lab-grown diamonds, which procedure is crucial for checking fluorescence?

UV radiation examination Signup and view all the answers

Which of the following is true regarding the growth of CVD diamonds?

CVD diamonds are formed without the stabilization of high pressures. Signup and view all the answers

What is one of the functions of the DiamondView in gemology?

To identify inclusions and growth features. Signup and view all the answers

What primarily causes the yellow color in type Ib HPHT lab-grown diamonds?

Incorporation of isolated nitrogen in the crystal lattice Signup and view all the answers

Which element is NOT typically used as a nitrogen getter in the synthesis of colorless HPHT diamonds?

Boron Signup and view all the answers

What is a common feature that gemologists examine to identify HPHT diamonds?

Fluorescence under UV radiation Signup and view all the answers

What type of graining pattern is characteristic of HPHT diamonds?

Cuboctahedral graining Signup and view all the answers

Which inclusions might indicate that a diamond is HPHT lab-grown?

Surface-reaching feathers and chips Signup and view all the answers

Which type of HPHT diamond is considered the rarest in nature?

Type Ib Signup and view all the answers

What aspect of HPHT diamonds contributes to their identification during microscopic examination?

Metallic inclusions from the growth process Signup and view all the answers

What must be removed from the chamber for producing colorless HPHT diamonds?

Nitrogen-containing air bubbles Signup and view all the answers

What mechanism primarily determines the growth patterns observed in HPHT diamonds?

Cuboctahedral arrangement of internal growth sectors Signup and view all the answers

What is the challenge associated with growing colorless HPHT diamonds?

High purity components and nitrogen removal are required Signup and view all the answers

Which components are essential for the CVD diamond synthesis process?

Gaseous carbon source, substrate, energy source, and heating element Signup and view all the answers

What is the main effect of adding low concentrations of nitrogen or oxygen to the gas mixture during CVD diamond growth?

It accelerates the diamond growth process Signup and view all the answers

What type of diamonds are the majority of CVD lab-grown diamonds classified as?

Type IIa Signup and view all the answers

What distinguishes polycrystalline diamonds formed in CVD environments?

They consist of many small interlocking diamond crystals Signup and view all the answers

Why are most CVD lab-grown diamonds unable to be identified using standard gem-testing equipment?

They mimic natural diamonds too closely Signup and view all the answers

What is the primary method developed for producing diamonds that involves simulating natural conditions?

High-Pressure, High-Temperature (HPHT) Signup and view all the answers

Which method was first successful in producing tiny diamonds before advancements were made in creating larger gems?

Chemical Vapor Deposition (CVD) Signup and view all the answers

What significant advancement in diamond synthesis occurred in 1970?

Production of the first cuttable gem-quality HPHT lab-grown diamonds Signup and view all the answers

What was the weight of the largest reported HPHT lab-grown diamond crystal reported in 1993?

34.80 carats Signup and view all the answers

Which company was instrumental in creating the first batch of industrial diamonds using the HPHT method in the 1950s?

General Electric Corporation (GE) Signup and view all the answers

What color range was produced by the early HPHT diamonds created in 1970?

F - J in color Signup and view all the answers

What aspect of diamond growth did William G. Eversole contribute to in 1952?

Production of tiny diamonds using CVD Signup and view all the answers

When did the jewelry industry start to accept lab-grown diamonds as a commercial product?

2003 Signup and view all the answers

Why were early attempts at creating gem-quality diamonds limited?

Technological limitations in producing larger crystals Signup and view all the answers

Which of the following colors did NOT appear in the HPHT diamonds produced by 2003?

Red Signup and view all the answers

What is the main characteristic of CVD lab-grown diamonds compared to HPHT lab-grown diamonds?

CVD diamonds require a lower probability of formation. Signup and view all the answers

What phenomenon is observed by using crossed polarizers on a diamond?

Visible strain patterns indicating stress. Signup and view all the answers

Which type of fluorescence is most commonly observed in HPHT diamonds under shortwave UV?

Greenish yellow to yellow fluorescence. Signup and view all the answers

What are bright interference colors in diamonds indicative of?

Heavy strain within the diamond. Signup and view all the answers

What is the role of the second polarizer when examining a diamond for strain?

To rotate and create a dark position. Signup and view all the answers

What characteristic differentiates HPHT diamonds from CVD diamonds in terms of luminescence?

HPHT diamonds have subdued interference colors. Signup and view all the answers

In terms of stability, why are diamonds produced through CVD growth considered metastable?

They can theoretically transform but remain stable over time. Signup and view all the answers

How does high pressure and temperature affect HPHT diamonds compared to CVD diamonds?

HPHT diamonds are formed under conditions similar to natural diamonds. Signup and view all the answers

What type of colors can be observed in HPHT diamonds under cross-polarized light?

Subdued colors such as white, gray, or black. Signup and view all the answers

What causes phosphorescence in specific HPHT diamonds?

The incorporation of boron within the diamond. Signup and view all the answers

Study Notes

Lab Grown Diamonds

Two main methods for commercial lab-grown diamonds: High-Pressure, High-Temperature (HPHT) and Chemical Vapor Deposition (CVD).
Early research: focused on industrial diamonds.
1797: English chemist Tennant proved diamond is pure carbon.
1800s-1900s: Researchers struggled to create diamonds; lacked suitable technology.
1941: Bridgman (American researcher) joined GE for high-pressure physics research.
1952: Scientists experimented with the CVD method.
1954: GE created initial industrial diamonds using HPHT.
1955: GE announced HPHT achievement.
1970: First cuttable gem-quality HPHT diamonds created (1-carat).
1990s: Japan (Sumitomo), GE, and De Beers produced larger, near-colorless HPHT diamonds.
1993: Largest HPHT crystal (34.8 ct.) produced.
2003: Jewelry industry started accepting lab-grown diamonds commercially; various colors (yellow, blue, green, pink).
2003: CVD method for gem-quality diamonds; predominantly brown, smaller due to limited thickness.
2007: Wide range of CVD colors (colorless-near-colorless, orange, pink, brown)
2014: Russian company NDT produced large colorless, faceted HPHT diamonds (> 5.11 ct).
2015: NDT made a 10.02-ct. colorless, VS-clarity faceted HPHT diamond from a 32.26-ct rough.
2018: US FTC amends Guides for Jewelry industry.
2019: CIBJO creates Lab-Grown Diamond Committee.
2018: US FTC amends Publications.
2018: US FTC Guidance.
2018: U.S. Federal Trade Commission publication revised

Industrial Applications

Tools and equipment embedded with lab-grown diamonds for various uses: machining car components, cutting natural hardwoods, granite, and marble; as drill bits, machining tools, and saws; used for engraving on glassware; fine surgical procedures.

HPHT Synthesis

Mimics the earth's natural diamond creation process (high temp & pressure).
Uses carbon source (graphite or diamond powder) converted into diamond under high pressure (5-6 GPa).
Temperatures range from 1300-1600°C.
Diamond growth time varies from days to weeks, dependent on size goal.
Metal catalyst (iron, nickel, cobalt, titanium, etc.) used to reduce temperatures and pressures for faster growth.
Various press designs exist (cubic, BARS, toroid) with differences in anvil numbers and sizes affecting pressure capacity and the size of the resulting diamond.

CVD Synthesis

Growth at lower pressure and temperatures compared to HPHT
Metastable conditions - diamond theoretically unstable but stable over time
Uses a hydrocarbon gas (methane), hydrogen gas, substrate, energy source & a heating element.
Growth within a vacuum chamber using a substrate (natural or lab-grown) as a template.
Gas molecules broken down into carbon atoms via an energy source (microwave plasma).
CVD diamonds form in layers (terrace/riser growth), creating a polycrystalline appearance if not treated.

Diamond Types (HPHT & CVD)

Type IIa diamonds are most common; colorless-near colorless are difficult to achieve
Color zoning, strain patterns, impurities, growth sectors (cuboctahedral) used for identification.
Natural diamonds also have imperfections, but they tend to have different patterns and distributions.
Lab crystals sometimes have strain that results in interference colors; natural diamonds exhibit very clear patterns under these special conditions.

Diamond Identification

Standard gem-testing equipment might not identify lab-grown diamonds.
Skilled gemologists use microscopes, UV radiation, and strain observation techniques.
Characteristics like inclusions, fluorescence, and graining assist in assessing type and origin.
GIA provides synthetic diamond grading reports.

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Description

Explore the fascinating history and methods of lab-grown diamonds, focusing on the High-Pressure, High-Temperature (HPHT) and Chemical Vapor Deposition (CVD) techniques. Learn about key milestones in their development from industrial applications to their acceptance in the jewelry market. This quiz delves into the advancements that have made lab-grown diamonds a viable alternative to natural diamonds.