Simulant peridot

[Niel]

Would a refractometer (is that a thing?) Be a sufficient way to tell if something is genuine peridot? Would something more be needed?

 

[Michael_E]

Would a refractometer (is that a thing?) Be a sufficient way to tell if something is genuine peridot? Would something more be needed?

Yes, something more is needed. What's needed depends upon how sure you want to be and what sort of indicators you have. I would also test for specific gravity, optic character and pleochroism. If you have a loupe and the sample has lilypad inclusions, the right color range and some facet doubling in certain directions, you can be pretty sure that it's peridot, (since glass doesn't have those sorts of inclusions, tourmaline usually has more distinct dichroism and other stones are often more dense without those lilypads). No inclusions means more testing.
You can also try some of the techniques of "Visual Optics" popularized by Alan Hodgkinson. John Bailey has a really good little post on part of these techniques here: http://facetingacademy.com/learn-faceting/learn-faceting-free/gem-identification/