Formula: Na₂Zr(Si₃O₉) · 2H₂O

Species:

Colour: Dark brown, reddish brown, flesh red, yellowish red, colourless, light grey, beige to tan, light yellow, orange, light blue

Lustre: Vitreous, Dull

Hardness: 5½ – 6

Specific Gravity: 2.65 – 2.9

Crystal System: Monoclinic

Member of: Catapleiite Group

Name: First described in 1850 from Låven, Langesundsfjorden, Norway by the Norwegian mineralogist Paul Christian Weibye (1819-1865). It was found by him the year before, in 1849. The name is from the Greek κατα = ‘with’ and πλειον = ‘more’ and refers to its association with many other rare minerals.

Type Locality: Låven, Langesundsfjorden, Larvik, Vestfold og Telemark – Norway

Dimorph of: Gaidonnayite. The monoclinic dimorph of gaidonnayite. The sodium analogue of calcium-catapleiite.