Identify

Drag a line across something in the photograph whose size is known — a coin, a bank card, an AA cell — then say what it is. Without that the picture cannot be measured, only looked at.

The 129 candidates above are the ones identifiable by field tests — the rest of the six thousand described mineral species need X-ray diffraction, not a hand lens, so putting them in a scratch-test key would be dishonest. But any of them can be looked up here, from the encyclopaedia and the lithology registry, whenever there is a connection.