Striz Radium Rock (ca. 1930)
This device belongs to a category of devices know as emanators that were placed in water, usually 1-2 gallons, to infuse the water with radon, a radioactive gas.
It is very similar in appearance to the Hammer Radium Activator used in the Radium Water Jar. Whether the Striz Radium Rock originally came in a jar, or whether it was a stand alone device such as the Thomas Cone, is not known.
As a guess, I would say that the radioactive component, either uranium ore or purified radium, was mixed throughout the matrix of the device.
Size: 3.75" diameter, 1.9" high
Exposure rate: 20 uR/hr above background at one foot
Donated by the State of Michigan courtesy of Theodore Wentworth.