Home > Pseudomorphs – March 3 > MS1521 Achtaragdite: Grossular after Wadalite

Achtaragdite: Grossular after Wadalite - Sold

These pseudomorphs have puzzled mineralogists since the mid 19th century. They have a very distinctive form, and show all aspects of full tetrahedral symmetry (43m point group). They consist of fine-grained hydroxylated grossular, and contain no relict traces of their original mineral. Glocker lists Achtaragdit in his 1847 Generum et Specierum Mineralium Synopsis. Breithaupt (1866) suggests helvite, a manganese beryllium silicate, for the original mineral. Notably, there is no manganese staining in these crystals or their matrix; it does not take much manganese oxide to stain crystals black... Prendel (1889) postulates boracite, magnesium borate, for the precursor. Pekov (1998) finally suggests wadalite, a calcium aluminum silicate. A nice example with a bit of attached matrix. Not so common on the mineral market.