How can a jeweler tell the difference between diamond and cut glass?

Answer 1

The jeweler will test the jewel with a probe: the probe indicates whether or not and how electricity reacts with the jewel, to determine whether it is a diamond or (most) anything else.

A jeweler will use a probe to verify that a diamond is a diamond and not cut glass.

Answer 2

There are several things a jeweller could look for to distinguish diamonds from glass. Diamonds:

• have a specific gravity of 3.5 g
  
• fluoresce blue in ultraviolet light
  
• have a hardness of 10 on the Mohs scale
  
• have refractive index of 2.418 (at 500 nm)

Using just his senses an experienced gemologist would notice:

• Glass is non-crystalline whereas diamond is crystalline.
  
• Glass is more transparent than diamond.
  
• Diamonds come with carbon flaws. On the contrary, glasses are flawless.
  
• The angle of cuts in a paste gem are different than a diamond, this would be obvious.

Answer 3

There are several things a jeweller could look for to distinguish diamonds from glass. Unfortunately some diamond substitutes like moissanite, quartz and others can pass some of the tests. Diamonds:

• have a specific gravity of 3.5 g
  
• (some but not all) fluoresce blue in ultraviolet light due to the presence of boron. This may not be good as transparency my be less with stronger florescence
  
• have a hardness of 10 on the Mohs scale
  
• have refractive index of 2.418 (at 500 nm)

Using just his senses an experienced gemologist would notice:

• Some jewellers see if they can read through a diamond. the high refractive index lets them read through glass, but not diamonds
• Some may breathe on cold diamonds to see if they fog - glass forms a persistent haze, diamonds don't due to high thermal conductivity
• Glass is non-crystalline whereas diamond is crystalline.
  
• Glass is more transparent than diamond.
  
• Diamonds come with carbon flaws. On the contrary, glasses are flawless.
  
• The angle of cuts in a paste gem are different than a diamond, this would be obvious.

Some jewellers use a "diamonds probe". There are two types of this device. The first seeks to measure the thermal conductivity of the diamond which is higher than most imitation diamond materials. Other probes use electrical resistance. Natural diamonds are good insulators while many made stones are conductors due to a layer of hydrogen at the surface.

Answer 4

A jeweler can distinguish between a diamond and cut glass by using a loupe to examine the facets and edges. Diamonds have unique characteristics such as brilliance, fire, and scintillation that are not present in cut glass. Additionally, a jeweler can also perform tests like the scratch test or the fog test to confirm the authenticity of a diamond.