Ass #16 - Key Terms and Concepts

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What is a catalyst in a chemical reaction?

A method of diamond synthesis at high temperatures

A substance that decreases the rate of a reaction

A solid carbon source used in diamond growth

A substance that increases the rate of a chemical reaction (correct)

What distinguishes crossed polarizers from regular polarizers?

They amplify the intensity of transmitted light.

They transmit unpolarized light.

They transmit light in parallel directions.

They are aligned perpendicularly to block light. (correct)

Which factors must lab-grown diamond producers consider?

Market demand for mined diamonds

Supply of natural diamonds

Equipment capacity and growth time (correct)

Geological conditions for natural diamond formation

Which method is known for synthesizing lab-grown diamonds that replicates the earth’s natural processes?

High-pressure, high-temperature (HPHT) Signup and view all the answers

What characteristic does a cuboctahedron exhibit?

A mix of both octahedral and cubic faces Signup and view all the answers

What is a primary challenge in removing isolated nitrogen from HPHT lab-grown diamonds?

It is extremely difficult to remove. Signup and view all the answers

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

Type IIa Signup and view all the answers

Which of the following statements about HPHT diamonds is true?

They generally exhibit stronger fluorescence to shortwave UV. Signup and view all the answers

What type of internal inclusion might be present in HPHT lab-grown diamonds?

Remnants of the metal catalyst used in the growth Signup and view all the answers

Which process is used to convert a gaseous carbon source into diamond?

Chemical vapor deposition Signup and view all the answers

How are interference colors in diamonds produced?

Through the interaction of two light rays under cross-polarized light Signup and view all the answers

What is required for growing diamonds using the CVD process?

A gaseous carbon source and hydrogen gas,a substrate, an energy source, and a heating element. Signup and view all the answers

What are the visible growth sectors called in CVD lab-grown diamonds?

Terraces and Risers Signup and view all the answers

Which diamond type saw limitations in jewelry use until recently due to high production costs?

Both High-pressure, high-temperature (HPHT) & Chemical vapor deposition (CVD) Signup and view all the answers

Why must most CVD lab-grown diamonds be submitted to a laboratory for identification?

They are often mistaken for natural diamonds. Signup and view all the answers

What feature of CVD lab-grown diamonds is rarely observed under longwave UV light?

Fluorescence Signup and view all the answers

What characteristic shape do rough CVD diamonds typically resemble?

Slabs with a square cross-section Signup and view all the answers

What should be done if there is uncertainty regarding a stone's identity?

Submit it to a gemological laboratory. Signup and view all the answers

What aspect of diamond screening devices is based on natural diamonds primarily being type Ia?

The characteristics of screening methods Signup and view all the answers

What does the grading process for lab-grown diamonds involve?

The same rigorous grading process as natural diamonds Signup and view all the answers

Manufactured diamond with essentially the same physical, chemical, and optical properties as natural diamond is ........

Laboratory-Grown (lab-grown) Diamonds Signup and view all the answers

A three-dimensional region with a common crystallographic growth plane....

Growth Sector Signup and view all the answers

Theoretically unstable but regarded as stable due to its longevity..........

Metastable Signup and view all the answers

A plastic disk embedded with specifically oriented microscopic crystals, designed to transmit polarized light........

Polarizer Signup and view all the answers

A template or seed for new CVD diamond growth......

Substrate Signup and view all the answers

The characteristic terrace and riser growth sectors in CVD lab-grown diamonds can be seen .......

can be seen with a DiamondView. Signup and view all the answers

The appearance of many colorless and colored CVD lab-grown diamonds is due to ......

to post-growth treatment Signup and view all the answers

CVD diamond growth occurs at ........

very low pressures and moderate temperatures. Signup and view all the answers

Blue and colorless HPHT lab-grown diamonds often show .........

green-blue phosphorescence. Signup and view all the answers

Which lab-grown diamonds never show any clear strain patterns?

HPHT Signup and view all the answers

The interference colors in diamonds reflect the .....

the intensity of the strain. Signup and view all the answers

Colorless HPHT lab-grown diamonds are.....

type IIa or weak type IIb. Signup and view all the answers

HPHT diamond crystal growth is predominantly ......

cuboctahedral Signup and view all the answers

Growing diamonds with the HPHT process requires ....

a carbon source, heating element, metal catalyst, seed crystal, and temperature gradient. Signup and view all the answers

The two major commercial technologies for synthesizing lab-grown diamonds are ......

the high-pressure, high-temperature (HPHT) and chemical vapor deposition (CVD) methods. Signup and view all the answers

HPHT lab-grown diamonds are produced by converting a solid carbon source to diamond .....

with an HPHT press. Signup and view all the answers

The lab-grown diamonds used in jewelry before 2010 were primarily ......

primarily colored and produced in small sizes. Signup and view all the answers

Diamond synthesis research began before 1800, but diamonds weren’t grown in the lab until ......

the 1950s. Signup and view all the answers

Study Notes

Key Terms and Concepts

Catalyst: A substance that speeds up a chemical reaction.
Crossed Polarizers: Two polarizers aligned perpendicularly, blocking light.
Cuboctahedron: A crystal shape with both octahedral and cubic faces.
Growth Sector: A three-dimensional region with a shared crystallographic plane.
Interference Colors: Spectral colours from light interacting in a crystal.
Laboratory-Grown Diamonds: Diamonds with identical properties to natural diamonds, produced artificially.
Metastable: Seemingly stable, but potentially unstable in theory.
Polarizer: A material designed to transmit polarised light.
Substrate: A surface used as a template for diamond growth.

Key Concepts

HPHT and CVD methods: Two main technologies for growing lab-grown diamonds. High pressure, high temperature (HPHT) and chemical vapor deposition (CVD).
Historical Development: Diamond synthesis research has been ongoing since before 1800. Lab-grown diamonds weren't widely produced until the 1950s/early 2000s.
Early Production Limitations: High cost & small size/coloured diamonds limited early HPHT production in jewelry market.
Lab-Grown Diamond Considerations: Equipment capacity, growth time, and cost are key factors for lab-grown producers.
HPHT Process: Replicates earth's natural diamond formation, by converting a solid carbon source into a diamond using high pressure and high temperature.
HPHT Growth Factors: Carbon source, heating element, a metal catalyst, seed crystal, and temperature gradient are required to produce a diamond.
HPHT Characteristics: Primarily cuboctahedral shape, nitrogen isolation difficulties, type IIa or weak type IIb diamonds are colorless.
Internal Inclusions: Metal catalyst remnants are the only possible internal inclusions encountered in HPHT lab-grown diamonds.
Interference Colours: The intensity of the strain within the diamond reveals these observable colours.
Fluorescence: HPHT diamonds show stronger fluorescence in shortwave UV than longwave UV. Blue/colourless variety often shows green-blue phosphorescence.
CVD Process: Diamond growth at lower pressures and moderate temperatures, where a gaseous carbon source is transformed into diamond using a reactor.
CVD Factors for Growth: Gaseous carbon source, hydrogen gas, substrate, energy source, and heating element.
CVD Growth Sectors: Layers and sectors (terraces and risers) are common in CVD-grown diamonds.
CVD Diamond Characteristics: Rough slabs commonly in a square cross section, mostly Type IIa.
Post-Growth Treatment: Post-growth treatment affects appearance in most CVD lab-grown diamonds.
Identification Requirment: Accurate identification often needs to be done by a lab.
DiamondView: Device utilized to detect distinctive growth sectors of CVD diamonds under long-wave UV light.
Natural Diamond vs. Lab Grown: Lab-grown diamonds undergo the same rigorous grading process as natural diamonds.

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Description

This quiz covers key terms and concepts related to laboratory-grown diamonds, their properties, and the technologies used for their growth, including HPHT and CVD methods. Test your understanding of terms like catalyst, crossed polarizers, and interference colors, as well as the historical development of diamond synthesis.