Granulation is a jewelry manufacturing technique whereby a surface is covered in spherules or granules of precious metal. The technique is thought to have its origins in Sumer about 5,000 years ago. In the first millennium B.C. the technique was used by Etruscans living in present-day Italy. Greek craftsmen also employed the technique, but it was the work coming from Etruria which became famous, in part due to the mysteries surrounding the process.

Source: https://en.wikipedia.org/wiki/Granulation_(jewellery)