JOAQUINITE
Joaquinite is a rare, chemically complex
barium-titatnium-cerium silicate mineral (Ba2NaCe2FeTi2Si8O26(OH,F)·H2O).
In addition to cerium, other rare earth elements (REEs) have been reported from
joaquinite specimens, including lanthanum (La), neodymium (Nd), praseodymium
(Pr), samarium (Sm), and yttrium (Y). It has a nonmetallic luster, a
transparent yellowish to brownish color, a white streak, is moderately hard (H
= 5 to 5.5), has no cleavage, and forms tiny ~equidimensional crystals.
It is best known as a metamorphic mineral associated with benitoite, neptunite,
and natrolite in veins cutting through blueschists in San Benito County,
California, USA.
Joaquinite (orangish-brown) on blueschist (glaucophane metamorphite.
Right-hand crystal is 1 mm in size.