FIG. 69.—Pyron detector in which a fine wire is brought to bear against a crystal of iron pyrites.
Some of the many forms of detectors are interesting because of the ingenious manner in which equivalent results are attained. The illustration shows a type of detector known as the "Perikon." Two minerals, zincite (oxide of zinc) and chalcopyrites (copper-iron sulphide), are mounted in adjustable cups so arranged that the surfaces of the minerals can be brought into variable contact with one another.
FIG. 70.—Perikon detector.
Another very good rectifying detector is that consisting of a flat surface of highly polished silicon mounted in a small cup. A flat brass point mounted on the end of an adjustable thumbscrew is brought to bear on the silicon.
FIG. 71.—Silicon detector.
Other mineral detectors of value are the Pyron, molybenite and galena.
FIG. 72.—Electrolytic detector.