GEM ID Concepts Flashcards
Key Concepts
A materials optical density affects the speed of the light that passes through it.
A materials optical density affects the speed of the light that passes through it.
The higher a materials optical density, the smaller its critical angle and higher RI
The higher a materials optical density, the smaller its critical angle and higher RI
Single refractive stones give you only one RI reading
Single refractive stones give you only one RI reading
Most coloured stones are DR and give you two RI readings
Most coloured stones are DR and give you two RI readings
Because birefringence varies among DR gems, it can be an important identifying feature.
Because birefringence varies among DR gems, it can be an important identifying feature.
Yellow light with a wavelength of 589 nanometers is ideal for taking an RI
Yellow light with a wavelength of 589 nanometers is ideal for taking an RI
RI liquid is toxic so avoid contact with skin and use in a well ventilated area
RI liquid is toxic so avoid contact with skin and use in a well ventilated area
Well-polished gems with flat surfaces give the clearest, most accurate refractometer readings.
Well-polished gems with flat surfaces give the clearest, most accurate refractometer readings.
Always clean a stone before you test it with the refractometer
T or F
Use a pin head size of RI fluid to take RI readings
why?
Parallax might cause you to record a false RI or mistakenly identify and SR stone as DR, why?
Because wavering of RI readings between scale divisions can occur.
If the shade cutoff appears to jump when you rotate the polarising filter, the stone is DR.
If the shade cutoff appears to jump when you rotate the polarising filter, the stone is DR.
What does Birefringence prove and not prove?
It proves that a stone is double refractive, but its absence does not prove single refraction without further testing.
Unwanted light can mess with your RI readings, so always close the refractometers’ cover to block it out.
Unwanted light can mess with your RI readings, so always close the refractometers’ cover to block it out.
50/50 readings are typically the most accurate curved surface readings.
50/50 readings are typically the most accurate curved surface readings.
