Distinguishing method to find precious stones in small sample

摘要

Thermal conductivities of materials are compared using very small quantities in order to distinguish the precious stones without destroying them. This is performed by use of a thermocouple which is pressed into contact with the material after being heated. A thermal comparator comprises a thermocouple which is formed from two lengths of glazed constantin wire (10) and a short length of copper wire (11). A conical copper head (12) of small volume is welded to one junction and is pressed in use against the material sample. The copper wire and the two junctions are contained in a PVC sleeve (13) which slides in a glass tube (14). The constantin wires are glued (15) to the inside of the glass tube to form a spiral over part of their length. The ends of the wires are connected to a numerical millivoltmeter with high revolution.