Locality: Larderello, Pomarance, Pisa Province, Tuscany, Italy Dimensions: 6.1 cm x 3.7 cm x 2.2 cm An incredibly rare specimen of the borate larderellite from the type locality in Italy, Larderello in Tuscany which dates back to 1854 according to the label (it was described in Dana 5th ed. as bechilite in 1868). Larderellite is only found in two localities in the world, both in Italy, and is nearly impossible to find on the market today. The larderellites are the small white translucent crystals. This is the only piece of this material we've had and it comes with a classic label from Josef Vajdák/Pequa Rare Minerals. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Larderellite
Larderellite is an IMA-recognized mineral species in the borate class, with the chemical formula (NH₄)B₅O₇(OH)₂·H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/c). It is a member of the Larderellite structural group.
Key properties: specific gravity 1.905; optically biaxial.
IMA symbol Ldr, grandfathered status — known before the IMA’s founding, named in 1854.
Found in boric-acid-rich fumarolic lagoons.
It is found associated with Sassolite, ammonioborite, santite.
The mineral was named to honor Francesco de Larderel (1848–1925), principal operator of the Tuscan borax works.