Fresnoite , Quartz Locality: Junnila mine, New Idria District, Diablo Range , San Benito County , California , USA ( Locality at mindat.org ) Size: 1.9 x 1.7 x 0.4 cm. Fresnoite is a rare barium, titanium silicate and this fine thumbnail is richly covered with lustrous, sharp, burnt-yellow, blocky, complex crystals to 6 mm perched on quartz matrix from a small find of this hard-to-get species. This is a particularly rich and showy specimen of this rare species from the 1998 find. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Fresnoite
Fresnoite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ba₂TiO(Si₂O₇).
It crystallizes in the tetragonal crystal system (space group P4bm).
Key properties: Mohs hardness 3–4; specific gravity 4.43; White streak; Vitreous luster; optically uniaxial.
IMA symbol Fno, IMA status: approved, named in 1964.
Disseminated in gneissic metamorphic rocks composed mainly of sanbornite and quartz (Rush Creek, California, USA).
It is found associated with Quartz, sanbornite, celsian, taramellite, diopside, pyrrhotite (Rush Creek, California, USA); bario-orthojoaquinite, benitoite, baotite.
The name refers to the original localities in Fresno Co., California, USA.