Methods and techniques

 

Wulff introduced at the beginning of the century, the use of the Wulff's net which one allowed the diffusion of the stereographic projection.

 

Verneuil developed in 1902 the " Verneuil’s process " to operate the anhydrous growth of crystals from the mineral powder melting in a flame. This will lead to a commercial success (corundum synthesis...).

 

Joly explains in 1907 the pleochroic halos visible around zircon inclusions inside micas as being due to radioactivity.

 

Boltwood, according to a proposal suggested by the eminent physicist E Rutherford, realised in 1907 the first estimation of the age of a mineral starting from analyses of its uranium and lead contents.

 

Winchell and Winchell published in 1909 their " Elements of optical mineralogy. "a significant treatise on microscopic petrography.

 

Fenner and Piggot published in 1929 the first determination of the age of a mineral starting from the contents of lead isotopes measured by mass spectrometry.

 

Goldschmidt suggested in 1937 that the radioactive decay of strontium and rubidium should be used for the age determination of minerals.