The original tag still shows the term mesitite, a disused synonym to indicate magnesite, the famous magnesium carbonate, but still valid to indicate samples with high iron content (for some this term indicates a variety of magnesite rich in iron). The splendid specimen illustrated in the figure comes from the well-known type deposits of Traversella, Ivrea, Piedmont, Italy, and consists of large lenticular crystals of iron-rich magnesite, grouped with crystallized hyaline quartz on white dolomite, with partial patina of ocher limonite and micaceous hematite .

One of the prides of the Sapienza Museum of Mineralogy is that it possesses one of the largest and richest collections in the world of samples extracted in Italy, often coming from mines that are now exhausted or inaccessible; this collection was made possible thanks to large acquisitions and donations which took place, as highlighted in this volume, in the pre-unification period of Italy.

This magnesite, purchased in 1852 by Monsignor Lavinio de 'Medici Spada, constitutes for its historical-scientific importance, and for its beauty, a backbone of this extraordinary collection of Italian minerals.