tourmaline tongs

noun plural but sometimes singular in construction

: a simple form of polariscope consisting of two transparent plates of tourmaline cut parallel to the optic axis and mounted on a tongs-shaped support so that the object to be examined can be held between them and used especially by jewelers for distinguishing glass from crystal

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

• More than 250,000 words that aren't in our free dictionary
• Expanded definitions, etymologies, and usage notes
• Advanced search features
• Ad free!