Posnjakite

Posnjakite specimen
Image credit: Leon Hupperichs

Description

A blue-green mineral that has been occasionally found as a pigment. Posnjakite occurs naturally in deposits of Malachite. Recipes for the synthetic preparation of posnjakite are given in a late 18th century paint manual (Naumova and Pisareva, 1994). Posnjakite has also been found as a Bronze corrosion product where it is thought to be a precursor to Brochantite formation (Selwyn, et al., 1996).

Raman spectrum of Posnjakite; Credit: RRUFF

Synonyms and Related Terms

Posnnakit (Deut.)

Physical and Chemical Properties

• Composition = Cu₄SO₄(OH)₆-H2O
• Description = green blue to dark blue scaly crystals
• Luster = vitreous
• Hardness = 2 - 3
• Density = 3.4

Resources and Citations

• M.Naumova, S.Pisareva,"A Note on the Use of Blue and Green Copper Compounds in Paintings" Studies in Conservation 39:277-283, 1994.

• L.Selwyn, N.Binnie, J.Poitras, M.Laver, D.Downham, "Outdoor Bronze Statues: Analysis of Metal and Surface Samples" Studies in Conservation 41:205-228, 1996.

• Wikipedia: [1] accessed Dec 2022

• Webmineral: Posnjakaite