PbCO3PbOH2

PbCO3PbOH2 is a basic lead carbonate with the chemical formula Pb3(CO3)2(OH)2, commonly called hydrocerussite. It represents the combination of lead(II) carbonate with lead(II) hydroxide in a 2:1 ratio of carbonate to hydroxide, yielding a relatively dense, carbonate-rich lead mineral.

Occurrence and formation: Hydrocerussite occurs as a secondary mineral in the oxidation zones of lead ore deposits. It is often found together with cerussite (PbCO3) and anglesite (PbSO4). It forms through weathering and alteration of primary lead minerals and can appear as white to grayish masses or crystals in veinlets and mantles.

Structure and properties: In hydrocerussite, lead centers are coordinated by carbonate and hydroxide groups, forming a dense structure typical of basic lead carbonates. The mineral is relatively soft and has a high lead content, giving it a pale to white appearance with a resinous to adamantine luster in crystals. It is insoluble in water and dissolves in acids with release of carbon dioxide and lead ions. It commonly exhibits habit in prismatic or tabular crystals, though many specimens are granular masses.

Occurrence and uses: Basic lead carbonates have historical significance as components of the white lead pigment used in paints, though their use has declined due to toxicity concerns. Naturally occurring hydrocerussite is of interest primarily to mineral collectors and as a polymorph in the study of lead-bearing minerals.

Safety: Lead compounds, including basic carbonates like hydrocerussite, are toxic. Handling should minimize dust generation and exposure, and disposal should follow appropriate hazardous-w waste regulations to prevent environmental contamination.