Axinite or assinite, as reported on the original tag, brown in large crystals with albite and epidote on green schist, from St. Cristophe en Oisans, Isere, France.

Axinite is part of a group of borosilicates characterized by the presence of Ca and Al, has pyroelectric and piezoelectric properties and is very difficult to meet in samples of good quality and size due to its rarity and the difficulty of extraction and storage. (due to the fragility of the crystals). The specimen of axinite described here, which arrived in the Museum of Mineralogy in the Spada collection in 1852, is a splendid exception.

The sample has an absolute aesthetic value, where the axinite crystals, from transparent to translucent, are characterized by a perfect triclinic dress (one of the rarest in nature) and by an attractive brown color that turns to violet due to a strong pleochroism visible to the naked eye (properties of some minerals, which show different colors depending on the orientation of the crystal). To increase the importance of the sample illustrated in the figure is its origin: this example comes from excavations carried out in the nineteenth century in St Christophe-en-Oisans, a famous type locality for axinite, where the deposits are currently exhausted. The essence of the museum is therefore splendidly concentrated in this axinite: 1) the historical importance that translates into observing minerals that can no longer be extracted, 2) being able to enjoy the most beautiful pieces among those still around, coming from mines exhausted.