listvenite

thumb|A quarry of listwanite in the region of [[Aosta Valley, in Italy]] thumb|upright|A quarry of listwanite in the region of Aosta Valley, in Italy Listwanite (also sometimes spelled listvenite, listvanite, or listwaenite) is a rock type that forms when the groundmass of ultramafic rocks, most commonly mantle peridotites, is partially altered to carbonate minerals and cut by ubiquitous carbonate veins containing one or more of magnesite, calcite, dolomite, ankerite, and/or siderite. Original pyroxene and olivine in the peridotite are commonly altered to Mg- or Ca-carbonate and hydrous Mg-silicates, such as serpentine and talc. Complete carbonation of peridotite means that every single atom of magnesium and calcium as well as some of the iron atoms have combined with CO2 to form secondary carbonate minerals such a magnesite, calcite, and siderite, while the remaining silica atoms, formerly found in pyroxene and olivine (prior to alteration), are found in quartz, serpentine, and talc. Thus, in terms of bulk mineralogy, listwanites consist primarily of quartz (often of a rusty red colour), carbonate, serpentine, talc, ± mariposite/fuchsite (i.e., Cr-muscovite) ± gold.

==Formation== Geologists are still studying how listwanites form, but they likely form through the reaction of CO2-rich fluids with peridotites at approximately 50 to 200 °C. Faults and fractures permit the percolation of the CO2-rich fluids through peridotite, so the formation of listwanites is generally considered to be structurally controlled.