Hulsite Locality: Brooks Mountain, Seward Peninsula , Nome Borough, Alaska , USA ( Locality at mindat.org ) Size: miniature, 4.9 x 4.0 x 3.2 cm Hulsite Hulsite is an extremely rare iron borate, reported back in the 1890s. I have seen only half a dozen specimens for sale in my life, of which this is the largest and richest by far. All I have seen came from the same locality, its type locality. This piece is rich in massive and microcrystalline material. Ex. John White Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Hulsite
Hulsite is an IMA-recognized mineral species in the borate class, with the chemical formula Fe²⁺₂Fe³⁺O₂(BO₃).
It crystallizes in the monoclinic crystal system (space group P2/m). It is a member of the Hulsite structural group.
Key properties: Mohs hardness 3; specific gravity 4.28–4.57; Black streak; Submetallic to vitreous luster.
IMA symbol Hls, grandfathered status — known before the IMA’s founding, named in 1908.
Very rare, in a contact-metamorphosed limestone, close by an intrusive granite.
It is found associated with Calcite, vesuvianite, magnetite, garnet, fluorite, diopside.
The mineral was named to honor Alfred Hulse Brooks (1871–1924), geologist in charge of the Division of Alaskan Mineral Resources, U.S. Geological Survey.