57769560_s_Facet_Rough___PrettyRock_com__Fact
[#] 1 [Myth] All spectroscopes have wavelength scales. [Fact] 
Most gemological spectroscopes do not; the wavelength scale requires a 2nd tube.
Gemology, Gem Rough,Gemology,Gem Identification Tools,Facet Rough - PrettyRock.com
Fact