New structural data on Belgian Ardennites

Ardennite is a Mn-rich silicate mineral which contains arsenate and/or vanadate groups. This mineral was first discovered in a quartz vein in Salmchâteau (Ardennes, Belgium), in association with apatite and albite. The two mineral species, ardennite-(As) and ardennite-(V), are occurring in highly oxidized and manganiferous metasediments that were affected by low- to high-grade metamorphism (1). The general formula of ardennite may be written as A4M6T6O22(OH)6. The large A sites mainly contain Mn2+ and smaller amount of Ca2+ and Mg2+, the octahedral M sites can host Al3+, Fe3+, Mn3+, Mg2+ and o... Mehr ...