- Chemistry: (K, Na)3(Mn, Fe)7(Ti,
OH)7, Potassium Sodium Manganese Iron Titanium Niobium
- Class: Silicates
- Subclass: Inosilicates
- Group: Astrophyllite
- Uses: Only as mineral 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,
- 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,
- Notable Occurrences include the Kola Peninsula, Russia and Mt St.
Hilaire, Quebec, Canada.
- Best Field Indicators: brittleness, cleavage, color, luster and