Joaquinite-(Ce) is a rare silicate mineral with the chemical formula NaBa<sub>2</sub>Ce<sub>2</sub>Fe<sup>2+</sup>Ti<sub>2</sub>Si<sub>8</sub>O<sub>26</sub>(OH)÷2H<sub>2</sub>O. It crystallizes in the monoclinic system with orthorhombic pseudomorphism and exhibits tabular crystals.
Joaquinite-(Ce) belongs to the monoclinic crystal system with orthorhombic pseudomorphism. It forms in point group 2. Twinning is polysynthetic on {001}, and the mineral shows good cleavage on {001} with uneven fracture. The average hardness is 5.5 on the Mohs scale.
The mineral is translucent, with a vitreous lustre and white streak. It is biaxial and displays strong red-brown pleochroism. Internally, it shows strong red-brown reflections under crossed polars.
Joaquinite typically occurs in natrolite veins cutting a glaucophane schist, as inclusions in a serpentinite body, and in fennitized gneisses and alkalic syenites.
It is commonly found in association with aegirine, barylite, benitoite, eudialyte, natrolite, neptunite, and orthojoaquinite-(Ce).
Minerals with optical similarities include verplanckite, baotite, cerchiaraite, titantaramellite, taramellite, nagashimalite, strontiojoaquinite, strontio-orthojoaquinite, bario-orthojoaquinite, and orthojoaquinite-(LaâÂÂCe).
The type locality for joaquinite is the Dallas Gem Mine in the Benitoite Mine in California, USA.