In order to dissolve minerals from its compound that are suitable for radiometric dating and to get rid of their adhesions in the best possible way, the stone is ground several times with the jaw crusher and the roller mill. The minerals suitable for the chosen dating methodology are separated using density differences, magnetic properties and grain shape. Subsequently, the millbase is sieved; the finer grain fraction is of interest for further processing.
The Wilfley wet-shaking hearth …

Tephra, the Greek word for ash, is used to describe any material that is ejected by a volcano into the atmosphere (pyroclasts). Tephra includes dense blocks and bombs (> 64 mm), and lighter materials such as scoria, pumice and ash (< 2 mm). As one moves away from a volcano, the tephra deposits become finer grained (smaller particles) and thinner. This is because small airborne particles hover longer and stay within the atmosphere for a greater distance from the volcano. These particles of ash …