CHAPTER 16 KEY CONCEPTS & TERMS

Question 1

What are the two major commercial technologies for synthesizing lab-grown diamonds?

Answer 1

High-pressure, high-temperature (HPHT) and chemical vapor deposition (CVD) methods

Question 2

When did diamond synthesis research begin?

Answer 2

Before 1800

Question 3

In what decade were diamonds first grown in the lab?

Answer 3

1950s

Question 4

What limited the use of lab-grown diamonds in jewelry from the 1990s to the early 2000s?

Answer 4

High production costs

Question 5

What type of lab-grown diamonds were primarily used in jewelry before 2010?

Answer 5

Colored and produced in small sizes

Question 6

What factors must lab-grown diamond producers consider?

Answer 6

• Equipment capacity
• Growth time
• Costs

Question 7

How are HPHT diamonds grown?

Answer 7

In conditions that replicate the earth’s natural process

Question 8

What is required to produce HPHT lab-grown diamonds?

Answer 8

• Solid carbon source
• Heating element
• Metal catalyst
• Seed crystal
• Temperature gradient

Question 9

What is the predominant crystal growth shape of HPHT diamonds?

Answer 9

Cuboctahedral

Question 10

What is extremely difficult to remove from HPHT lab-grown diamonds?

Answer 10

Isolated nitrogen

Question 11

What types are colorless HPHT lab-grown diamonds?

Answer 11

Type IIa or weak type IIb

Question 12

What kind of inclusions might an HPHT lab-grown diamond contain?

Answer 12

Remnants of the metal catalyst it grew in

Question 13

What do interference colors in diamonds reflect?

Answer 13

The intensity of the strain

Question 14

Do HPHT lab-grown diamonds show clear strain patterns?

Answer 14

No

Question 15

How do HPHT lab-grown diamonds generally react to UV light?

Answer 15

Stronger fluorescence reaction to shortwave UV than to longwave UV

Question 16

What phosphorescence do blue and colorless HPHT lab-grown diamonds often show?

Answer 16

Green-blue phosphorescence

Question 17

At what conditions does CVD diamond growth occur?

Answer 17

Very low pressures and moderate temperatures

Question 18

How are CVD diamonds grown?

Answer 18

By converting a gaseous carbon source to diamond using a reactor

Question 19

What is required to grow diamonds using the CVD process?

Answer 19

• Gaseous carbon source
• Hydrogen gas
• Substrate
• Energy source
• Heating element

Question 20

How do CVD diamonds grow?

Answer 20

Layer by layer through a series of steps known as terraces and risers

Question 21

What does CVD diamond rough resemble?

Answer 21

Slabs with a square cross section

Question 22

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

Answer 22

Type IIa

Question 23

What affects the appearance of many colorless and colored CVD lab-grown diamonds?

Answer 23

Post-growth treatment

Question 24

How can most CVD lab-grown diamonds be identified?

Answer 24

Must be submitted to a laboratory for identification

Question 25

Is it common for CVD lab-grown diamonds to fluoresce under longwave UV?

Answer 25

No, it is extremely rare

Question 26

What can be seen with a DiamondView in CVD lab-grown diamonds?

Answer 26

Characteristic terrace and riser growth sectors

Question 27

What is the basis for most diamond screening devices?

Answer 27

The majority of natural diamonds are type Ia

Question 28

What should you do if you are not certain of a stone’s identity?

Answer 28

Submit it to a gemological laboratory for identification

Question 29

How do lab-grown diamonds undergo grading compared to natural diamonds?

Answer 29

The same rigorous grading process

Question 30

What is a Catalyst?

Answer 30

A substance that increases the rate of a chemical reaction. ## Footnote Catalysts are not consumed in the reaction and can be reused.

Question 31

What are Crossed polarizers?

Answer 31

Two polarizers with their light-transmitting directions aligned perpendicularly so light cannot transmit through them. ## Footnote This setup is often used in optical experiments to analyze light properties.

Question 32

Define Cuboctahedron.

Answer 32

A crystal with both octahedral and cubic faces. ## Footnote Cuboctahedra belong to the family of Archimedean solids.

Question 33

What is a Growth sector?

Answer 33

A three-dimensional region with a common crystallographic growth plane. ## Footnote Growth sectors are important for understanding crystal formation.

Question 34

What are Interference colors?

Answer 34

Spectral colors caused by the interaction of two light rays seen under crossed-polarized light. ## Footnote These colors result from the constructive and destructive interference of light waves.

Question 35

What are Laboratory-grown diamonds?

Answer 35

Manufactured diamond with essentially the same physical, chemical, and optical properties as natural diamond. ## Footnote Lab-grown diamonds are often indistinguishable from natural diamonds without specialized equipment.

Question 36

Define Metastable.

Answer 36

Theoretically unstable but regarded as stable due to its longevity. ## Footnote Metastable states can persist for long periods before transitioning to a more stable state.

Question 37

What is a Polarizer?

Answer 37

A plastic disk embedded with specifically oriented microscopic crystals, designed to transmit polarized light. ## Footnote Polarizers are commonly used in photography and LCD screens.

Question 38

What is a Substrate?

Answer 38

A template or seed for new CVD diamond growth. ## Footnote Substrates are crucial in the chemical vapor deposition (CVD) process for diamond synthesis.