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Natural Rock Sample System

Monitor RAD7 performance once a month.


The Natural Rock Sample system consists of a 21oz (600g) sample of granite gravel from a stone quarry, normally sold by the truckload as construction material. It is enclosed in a container that, by closing two ball valves, may be completely sealed.

Granite, in general, contains trace amounts of both uranium and thorium that has been in the rock since it was formed, millions if not billions of years ago. Therefore all the progeny of both the uranium and thorium decay chains are fully supported and in full equilibrium down to 226-Ra and 224-Ra.

The rock sample is dry and therefore constitutes a rock-steady emitter of both radon and thoron. It is possible to take advantage of that property to check the performance of a RAD7.

The device, as it stands, can provide a means for monitoring long-term changes in both radon and thoron sensitivity. After calibration at DURRIDGE Company, and with the optional Thoron Calibration Check Kit (sold separately), the device can be used for low-precision checking of both the RAD7's radon sensitivity (monthly) and its thoron sensitivity (any time). A copy of the Durridge-issued Natural Rock Sample Calibration Form can be previewed below.

Natural Rock Sample Physical Specifications

Shipping Dimensions

16" x 8" x 8" (41 cm x 20 cm x 20 cm)

Shipping Weight

5 pounds (2.3 kg)


Durridge Natural Rock Sample System User's Manual (PDF)

Sample Calibration Form (PDF)


Natural Rock Sample System Configuration Diagram (Illustration)

Natural Rock Sample System Components (Illustration)

Thoron Calibration Check Kit Components (Illustration)


Price List (HTML)

DURRIDGE Natural Rock Sample

Thoron Calibration Check Kit for Natural Rock Sample
(sold separately)

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