CGC Quality Assurance & Control 5

Question 1

A customer's appraisal states a diamond color one grade different from its lab report. What is the best response?

Accepted Answer

Explain normal grading tolerance and recheck the stone against master stones under standard lighting

Answer

A one-grade difference can fall within normal grader variation, and a controlled recheck settles it objectively.

Question 2

A thermal diamond tester reads "diamond" on a colorless stone. What should be done next?

Accepted Answer

Test with an electrical conductivity or moissanite tester and look for doubling

Answer

Moissanite conducts heat like diamond, so a second test is needed to rule it out.

Question 3

Which practice best guards against claims that a stone lost weight during repair?

Accepted Answer

Record the weight before and after service on the job ticket

Answer

Before-and-after weights give objective proof of the stone's condition.

Question 4

Before measuring a stone with a millimeter (Leveridge) gauge, what calibration step is needed?

Accepted Answer

Close the jaws and confirm the gauge reads zero

Answer

Zeroing removes offset errors that would affect every measurement.

Question 5

Which detail makes a gemstone grading record most auditable?

Accepted Answer

Date, grader ID, instruments used, lighting conditions, and photos

Answer

Traceable grading conditions let a reviewer reproduce and verify the result later.

CGC - Certified Gemstone Consultant Practice Test