• Chemistry: (K, Na)3(Mn, Fe)7(Ti, Nb)2(SiO3)8(O, OH)7, Potassium Sodium Manganese Iron Titanium Niobium Silicate Hydroxide.
  • Class: Silicates
  • Subclass: Inosilicates
  • Group: Astrophyllite
  • Uses: Only as mineral specimens.
  • Specimens

Kupletskite is a very rare manganese, titanium mineral found in some unusual rock assemblages called agpaitic pegmatites. It forms two solid solution series with the minerals astrophyllite and cesium-kupletskite. A solid solution series is where two or more minerals share the same structure, but vary their chemistry by specific limits. In these cases, astrophyllite and kupletskite vary in the amount of manganese and iron. Kupletskite is the manganese rich end member of the series and astrophyllite is the iron rich end member. Except for the minor change in chemistry, their structures are the same.

The mineral astrophyllite is the namesake of the mineral group to which all three minerals, kupletskite, astrophyllite and cesium-kupletskite belong; the Astrophyllite Group of minerals. The solid solution series between kupletskite and cesium-kupletskite involves the enrichment of the series with the element cesium in the potassium/sodium site of the structure. Cesium-kupletskite's formula is thus written as Cs3(Mn, Fe)7(Ti, Nb)2(SiO3)8(O, OH)7.


  • Color is bronze yellow or dark brown to black.
  • Luster is vitreous or submetallic to metallic, can be pearly on cleavage surfaces.
  • Transparency: crystals are translucent to opaque.
  • Crystal System is triclinic; bar 1
  • Crystal Habits include small tabular, acicular or bladed crystals. Also found in lamellar, micaceous or fibrous masses.
  • Cleavage is perfect in one direction, poor in another.
  • Fracture is uneven.
  • Hardness is 3.
  • Specific Gravity is 3.2 - 3.4
  • Streak is pale brown.
  • Associated Minerals are quartz, nepheline, microcline, albite, calcite, natrolite, fluorite, eudialyte, ancylite, arfvedsonite, micas and aegirine.
  • Notable Occurrences include the Kola Peninsula, Russia and Mt St. Hilaire, Quebec, Canada.
  • Best Field Indicators: brittleness, cleavage, color, luster and localities.
KUPLETSKITE specimens:
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KUPLETSKITE specimen kup-1
$ 65.00
Dims: 1.2 x 0.7 x 0.3" (3.0 x 1.8 x 0.8 cm)
Wt: 10.9 g w/ base
Mount Saint Hilaire, Quebec, Canada
This small specimen consists of a single, incomplete Kupletskite crystal. Though it is incomplete, it is undamaged and in excellent condition. The crystal itself makes up most of the dimensions of the specimen. Its triclinic, bladed form is rather poor, as only a few crystalline edges are visible, and all faces are incomplete due to growth inconsistencies. It has a dark brown coloration with paler, red-brown highlights and a dull pearly luster, and is essentially opaque. It is accompanied by a few incomplete bladed crystals that I cannot identify, and the piece is hot-glued onto a flat, square acrylic base.
no photo
kup-1 ($ 65.00)
Mount Saint Hilaire, Quebec, Canada
KUPLETSKITE specimen kup-2
$ 29.00
Dims: 1.35x0.92x0.71" (3.43x2.33x1.79cm)
Wt: 0.61oz (17.2g)
Gjerdingen, Norway
This thumbnail specimen contains numerous crystals, most noteably brown, transparent crystals of kupletskite. The largest kupletskite is adjacent to the largest aegirine crystal. There are more of each, although most of the easily visible crystals are aegirine. The host rock is an assemblage of tiny black aegirine and brown kupletskite crystals in a matrix that is mostly albite and quartz, although there are other minerals present, as well, including something pink.
no photo
kup-2 ($ 29.00)
Gjerdingen, Norway


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