Catapleiite is a rather rare zirconium mineral. It forms in alkaline rocks and rare rocks known as agpaites which are igneous rocks of unusual concentrations. They are characterized by high concentrations of alkali metals especially sodium and low concentrations of silicon and aluminum. They are feldspar and feldspathoid rich and being low in silicon, contain little or no quartz. Agpaite pegmatites contain unusual minerals because they originate with unusual elements. Elements such as beryllium, zirconium, titanium, niobium, barium, strontium, thorium and rare earth metals are all found in the compositional mix that represents this rock type.

There exists agpaite in several places around the world, but by far the most famous are the ones at the Kola Peninsula in Russia, Narsarsuk, Greenland and the one above all the rest, the mines of Mount Saint Hilaire, Quebec, Canada. Catapleiite is just one of the rare minerals that can form in these silica starved, unique chemical environments. Other minerals coming from these unique localities include leifite, synchysite, serandite, elpidite, aegirine, arfvedsonite, eudialyte and analcime to name a few.

Catapleiite is dimorphous with the mineral gaidonnayite. Dimorphous means that both minerals have the same chemistry, but they have different structures. Catapleiite is monoclinic (pseudohexagonal) while gaidonnayite is orthorhombic. Catapleiite is also in a series with the mineral calcium catapleiite in which the sodium of catapleiite is replaced with a calcium ion instead. In a series, the structure remains the same, but the chemistry is different.

Catapleiite although quite rare, forms at several localities around the world. But it is the magnificent specimens of rosette clusters found only at Mount Saint Hilaire that demonstrate the mineral's true beauty. Its rarity, beauty, unusual chemistry, classic locality and cool name make catapleiite a great addition to a mineral collection.


  • Color is blue, gray, pale yellow, yellowish-brown, reddish or colorless.
  • Luster is vitreous.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m.
  • Crystal Habits include pseudohexagonal plates or lamellar masses. Splendid rosettes are also known. Twinning is common.
  • Cleavage is perfect in one direction.
  • Hardness is 5 - 6.
  • Specific Gravity is 2.8
  • Streak is white.
  • Associated Minerals include feldspars, feldspathoids and Sphene among many rare species.
  • Notable Occurrences include Magnet Cove, Arkansas, USA; Madagascar; Laven, Langesundfjord, Norway and Mount Saint Hilaire, Quebec.
  • Best Field Indicators are crystal habit, locality and color.
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