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Yes, very handy devices called diamond testers quickly determine whether a diamond is genuine based on thermal conductivity.
A light pen is: a handheld, penlike photosensitive device held to the display screen of a computer terminal for passing information to the computer. That's a definition I got off the computer
If your asking what kind of cage you should get for your guinea pigs, then i recommend a C&C cage because you can make them any size (the minimum for 1 guinea pig is 7.5 square feet). They are very big and roomy. Do NOT get an aquarium, wire bottom cage, or a pet store cage. An aquarium can make your guinea pigs become blind. A wire bottom cage could injure your guinea pigs' feet and possibly break bones. And pet store cages are usually small and expensive.