Magnesite (Citron chrysoprase).

Magnesite (Citron chrysoprase).

Magnesite, MgCO3,  is a magnesium carbonate. The marketing name of citron chrysoprase is confusing, because chrysoprase is a silica mineral. This variety of magnesite gains its apple green colour from a nickel content, and for that reason is also called nickeloan magnesite.  This half nodule has been polished, and the outer skin shows  a deeper colour of green.  In the Western Australia gold field, which is the origin of this specimen, there are numerous  nodules,  sometimes as much as a ton in weight. To reiterate, although this variety of magnesite is called "Citron chrysoprase" it has no silica content.