THE MINERAL NARSARSUKITE

  • Chemistry: Na2(Ti, Fe)Si4(O, F)11, Sodium Titanium Iron Silicate Fluoride.
  • Class: Silicates
  • Subclass: Inosilicates
  • Uses: Only as mineral specimens and cut as gemstones for gemstone collectors.
  • Specimens

Narsarsukite is not a well known mineral, but it is a nice collection mineral. It is named for the wonderful mineral locality at Narsarsuk, Greenland, from where the first specimens were described in 1900. The locality is the result of agpaitic pegmatite intrusions, an unusual igneous rock that is high in alkaline metals (such as sodium) and poor in silica. These intrusions also contain a large number of unusual elements such as titanium, fluorine and rare earth metals.

Narsarsukite is also found at Mont Saint-Hilaire, Quebec; another agpaitic pegmatite location. Here is probably the best location for narsarsukite specimens as crystals are relatively large and well formed.

Narsarsukite has been cut as a gemstone, although do not expect to see it available in many jewelry stores. It is cut mostly for gemstone collectors, but is considered attractive. A cut stone of 0.31 carats was cut from the mines of Mont Saint-Hilaire, Quebec and is the largest known narsarsukite gemstone.

Narsarsukite's structure involves double chains of linked silicate tetrahedrons in a tube like arrangement. The chains are actually kinked into a what is best described as a "crankshaft" shape with the kinks going up and down like a crankshaft. The chemistry of narsarsukite may include yttrium, calcium and potassium, but they are not usually significant enough to include in the general formula.

PHYSICAL CHARACTERISTICS:

  • Color is various shades of yellow, green, pink and brown as well as colorless.
  • Luster is vitreous or adamantine to dull or greasy.
  • Transparency: crystals are transparent to translucent.
  • Crystal System is tetragonal.
  • Crystal Habits include tabular and prismatic crystals often arranged into sprays and parallel aggregates.
  • Cleavage is perfect in two directions (prismatic) and good in one direction (basal).
  • Fracture is uneven to subconchoidal.
  • Hardness is 6 - 7.
  • Specific Gravity is approximately 2.6 to 2.8
  • Streak is white.
  • Other Characteristics: Index of refraction: 1.601 - 1.614 and 1.632 - 1.647.
  • Associated Minerals are quartz, microcline, albite, amphiboles, carletonite, lorenzenite, calcite, leucosphenite, natrolite and aegirine.
  • Notable Occurrences include the type locality at Narsarsuk, Greenland and perhaps the best source of Mont Saint-Hilaire, Quebec, Canada as well as in north-central Montana, USA.
  • Best Field Indicators: Crystal habit, cleavage, color, associations and localities.
NARSARSUKITE specimens:
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NARSARSUKITE specimen nar-1
$ 25.00
Dims: 0.8 x 0.7 x 0.5" (2.0 x 1.8 x 1.3 cm)
Wt: 15.9 g w/ specimen box
Mount Saint Hilaire, Quebec, Canada
This thumbnail specimen consists of 2 tabular Narsarsukite crystals that are embedded in an agpaitic pegmatite host rock. The larger (and more visible) of these crystals has dimensions of 0.5 x 0.4 x 0.1" (1.2 x 1.1 x 0.2 cm) and is damaged and not quite complete. The smaller one, being better protected, is intact and in excellent condition. Both have good tetragonal bladed form, a dull, olive-green color and a pearly luster- the larger crystal might be aggregated with one or two other parallel crystals. They are both essentially opaque. The specimen is affixed inside a plastic specimen box with a removable putty.
no photo
nar-1 ($ 25.00)
Mount Saint Hilaire, Quebec, Canada
NARSARSUKITE specimen nar-2
$ 33.00
Dims: 1.0 x 0.8 x 0.7" (2.5 x 2.0 x 1.8 cm)
Wt: 19.7 g w/ specimen box
Mount Saint Hilaire, Quebec, Canada
Two small tabular Narsarsukite crystals are embedded in the pegmatite host of this thumbnail specimen. Each measures approximately 0.2 x 0.2 x 0.1" (5 x 5 x 1 mm) and is in very good condition- one shows light damage, but this damage does not appear to be fresh. Their tetragonal form is excellent, and both have a rather deep, olive-green coloration and a pearly luster. The piece is affixed inside a plastic specimen box with a removable putty.
no photo
nar-2 ($ 33.00)
Mount Saint Hilaire, Quebec, Canada
NARSARSUKITE specimen nar-3
$ 30.00
Dims: 2.12x1.47x0.58" (5.38x3.72x1.48cm)
Wt: 1.00oz (28.4g)
Lovozero Mine, Kola Peninsula, Russia
This is a specimen of narsarsukite, as a scattering of dull pale brown cubes in a gray host rock. The narsarsukite is weathered, less so on one side where the crystals are sharper. There are many cube shaped impressions in the host rock - they reveal the original shape of the narsarsukite crystals.
no photo
nar-3 ($ 30.00)
Lovozero Mine, Kola Peninsula, Russia
 

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