The detector utilizes a large-volume atomic-absorption technique for quantitative determinations of mercury vapor thermally released from crushed rock. A quartz-enclosed noble-metal amalgamative stage, which is temper at u r e controlled and is actuated by a radio-frequency induction heater, selectively traps the mercury and eliminates low-level contamination. As little as 1 part per billion of mercury can be detected in a 1-gram sample in a 1-minute analytical period.

The mercury content in soil gas and in the atmosphere was measured in several mining districts to test the possibility that the mercury content in the atmosphere is higher over ore deposits than over barren ground. At Cortez, Nev., the distribution of anomalous amounts of mercury in the air collected at ground level (soil gas) correlates well with the distribution of gold-bearing rocks that are covered by as much as 100 feet of gravel. The mercury content in the atmosphere collected at an altitude of 200 feet by an aircraft was 20 times background over a mercury deposit and 10 times background over two porphyry copper deposits. Measurement of mercury in soil gas and air may prove to be a valuable exploration tool.

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