Tourmaline tongs are a small, portable instrument widely used in mineralogy. The instrument was invented by Jean Baptiste Biot (1774-1862) who in 1815 had discovered dichroism, which is to say the property possessed by certain monoaxial, bi-refracting crystals to absorb ordinary rays in a way different from extraordinary rays.
The exemplar of the tongs in our collection surely dates back to before1872, the year in which it was inventoried; indeed, it comes from an old collection of instruments which had belonged to Professor Gian Pietro Radicati (Professor of Experimental Physics in Cagliari from 1853 to 1871), which was purchased by the Physics Laboratory at the time of his death.
It has an overall length of 19 cm, the disks containing the tourmaline are 4 cm in diameter with a central aperture of 1 cm; the tourmaline is of the green miscellaneousty.