Ground lapis lazuli was increasingly used by painters during the 13th and 14th centuries to make ultramarine and Cennino Cennini gives instructions on how to prepare this pigment in his “Book of Arts.” But it was not until the second half of the 16th century that large objects carved from lapis began to appear in Italy. The first center of production was Milan where the Miseroni brothers, Gasparo and Girolamo, became famous for their mastery of working this challenging material. Half a dozen of the pieces acquired by Grand Duke Cosimo I Medici are on show here, including the “Cup in the Form of a Shell” referred to in a letter of 1563.

https://www.nytimes.com/2015/08/19/arts/international/lapis-lazuli-and-the-history-of-the-most-perfect-color.html