Diamond Mate A/C

The Presidium Diamond Mate A/C is a handheld thermal-conductivity tester built for the everyday work of the jewellery counter. Press the retractable probe tip against a stone and the instrument measures how quickly that stone carries heat away — diamond conducts heat far faster than cubic zirconia, colourless sapphire, glass and the other simulants that circulate in the trade, so the LED readout and buzzer give a verdict in seconds. A spring-loaded tip applies the same pressure on every test, which is what makes repeat readings agree with each other, and there is no cool-down wait between stones, so a whole parcel can be checked in one sitting. At 160 × 21 × 30 mm it fits a shirt pocket, and the 0.6 mm tip — which Presidium states is the industry's thinnest — reaches into pavé and channel settings to test stones down to 0.02 ct, polished or unpolished, loose or mounted in an open-back setting. A metal alert buzzer tells you when the tip has slipped off the stone onto the metal, so you are never fooled by a reading taken on the mount. One limitation matters and Presidium states it plainly: moissanite conducts heat almost as well as diamond and will read as diamond on any thermal-only tester, so a moissanite check needs a separate electrical-conductivity instrument. Two variants share the same probe — PDMT-A runs on three AAA alkaline cells for about seven hours, PDMT-C on an inset rechargeable pack for about six hours or straight from the supplied 120/230 V adaptor. This is a contact instrument for the bench and the counter; it plays no part in searching ground for buried gold or stones.