Gemology Certification Gemology Gem Identification Techniques 4

Question 1

Which gemstone treatment is specifically detected by observing a 'flash effect' or blue/orange iridescence under magnification?

Accepted Answer

Fracture filling with glass

Answer

Glass fracture filling in rubies and emeralds produces a characteristic blue or orange flash effect under magnification with fiber-optic light.

Question 2

An alexandrite-like color change from green in daylight to red in incandescent light is caused by:

Accepted Answer

Chromium absorbing light selectively in the green-red transition zone

Answer

Chromium's absorption spectrum straddles the green-red boundary, causing alexandrite to appear green in balanced daylight and red under incandescent light.

Question 3

Which instrument measures the thermal conductivity of a gemstone to distinguish diamond from simulants?

Accepted Answer

Diamond probe (thermal tester)

Answer

Thermal testers (diamond probes) exploit diamond's exceptionally high thermal conductivity, which far exceeds most simulants including cubic zirconia.

Question 4

In gem identification, 'optic sign' refers to:

Accepted Answer

The positive or negative relationship of the optic axes in birefringent stones

Answer

Optic sign (positive or negative) describes the relationship between the ordinary and extraordinary rays in uniaxial stones, or the optic axes in biaxial stones.

Question 5

A green tourmaline showing strong pleochroism with colors of dark green and yellowish-green is being tested. What axis colors should a gemologist expect?

Accepted Answer

Dark green and light yellowish-green

Answer

Green tourmalines (verdelite) are strongly trichroic, most commonly showing dark green along one direction and lighter yellowish-green along another.

Gemology Certification Practice Test

Gemology Certification Practice Test

Gemology Certification Gemology Gem Identification Techniques 4