THE MINERAL ELPIDITE

  • Chemistry: Na2ZrSi6O15 - 3H2O, Hydrated Sodium Zirconium Silicate.
  • Class: Silicates
  • Subclass: Phyllosilicates
  • Uses: Only as mineral specimens.
  • Specimens

Elpidite is another in the long list of unusual mineral that come from agpaitic pegmatite rocks. Agpaitic pegmatite intrusions are unusual igneous rocks that are high in alkaline metals (such as sodium) and poor in silica. These intrusions also contain a large number of unusual elements such as zirconium. Elpidite was first discovered at Narsarsuk, Greenland, from where the first specimens were described in 1932. It is also found at Mont Saint-Hilaire, Quebec; another agpaitic pegmatite location. Mont Saint-Hilaire is undoubtedly the best location for elpidite specimens, as specimens from there form large sprays and interesting aggregates; and some specimens are fluorescent. Elpidite is a rare zirconium silicate mineral that can have a very nice crystal form and provide good specimens for micromounts and even larger cabinet specimens.

PHYSICAL CHARACTERISTICS:

  • Color is colorless, white, gray, tan to brick-red.
  • Luster is vitreous, earthy, dull or silky.
  • Transparency: Crystals are typically opaque to translucent or rarely transparent.
  • Crystal System is orthorhombic.
  • Crystal Habits include prismatic or acicular crystals often forming sprays or stibnite-like aggregates. Individual crystals can have sharp pointed terminations
  • Cleavage is good in two directions (prismatic).
  • Fracture is splintery or uneven.
  • Hardness is variable at 5 - 7.
  • Specific Gravity is approximately 2.5 to 2.6
  • Streak is white.
  • Other Characteristics: some specimens fluoresce green or yellow-green under shortwave UV light.
  • Associated Minerals are calcite, albite, bastnasite, apatite, rutile, pyrochlore, siderite, epididymite, chlorites, natrolite and aegirine.
  • Notable Occurrences include the type locality at Narsarsuk, Julianehaab district, Greenland and perhaps the best source for collection specimens is Mont Saint-Hilaire, Quebec, Canada. Also found at Langesundfjord, Norway.
  • Best Field Indicators: Crystal habit, color, cleavage, associations and localities.
ELPIDITE specimens:
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ELPIDITE specimen elp-1
$ 45.00
Dims: 1.8 x 1.7 x 1.3" (4.6 x 4.3 x 3.2 cm)
Wt: 1.3 oz. (38 g)
Mount Saint Hilaire, Quebec, Canada
Scores of individual Elpidite crystals and radiating Elpidite clusters intersect the white albite base of this hand specimen. These crystals reach lengths of about 1.2" (3.0 cm) and are generally in very good condition, as few of them show any obvious damage. Their orthorhombic form is a bit difficult to define, as individual crystals have a nearly fibrous, aggregated appearance, but is uniform throughout all of them. Their milky-white color is often dulled to a moderate gray, likely due to impurities, and all are translucent. A substantial amount of muscovite is embedded in the albite host, which is hot-glued to an acrylic base.
no photo
elp-1 ($ 45.00)
Mount Saint Hilaire, Quebec, Canada
ELPIDITE specimen elp-3
$ 75.00
Dims: 2.0 x 1.2 x 1.0" (5.0 x 3.0 x 2.5 cm)
Wt: 1.3 oz. (37 g)
Mount Saint-Hilaire, Quebec, Canada
Intersecting sprays of fine Elpidite needles make up the bulk of this hand specimen. These sprays are in very good condition, showing relatively light damage, and the needles therein reach lengths of 0.8" (2 cm). They are too fine and intergrown for one to effectively study their orthorhombic form, and all have a white color, though some show a brown discoloration. Their luster is pearly, and many are partially transparent. A few bits of what appear to be calcite are present, but there is no base rock. The Elpidite sprays glow a relatively bright green color under shortwave ultraviolet light.
no photo
elp-3 ($ 75.00)
Mount Saint-Hilaire, Quebec, Canada
ELPIDITE specimen elp-4
$ 68.00
Dims: 5.3 x 1.4 x 1.2" (13.4 x 3.7 x 3.0 cm)
Wt: 4.0 oz. (115 g)
Mount Saint-Hilaire, Quebec, Canada
This large cabinet specimen consists of a single spray of compact Elpidite crystals. This spray is in excellent condition and contains crystals of over 5" (12.7 cm) in length. The crystals are too tightly packed to show good orthorhombic form, and have a white color with a gray "marbled" discoloration and some apparent rust staining. Their luster is a dull pearly, and all are completely opaque. There is no host rock present.
no photo
elp-4 ($ 68.00)
Mount Saint-Hilaire, Quebec, Canada
ELPIDITE specimen elp-2
$ 170.00
Dims: 5.6 x 2.9 x 1.9" (14.1 x 7.3 x 4.9 cm)
Wt: 8.8 oz. (249 g)
Mount Saint-Hilaire, Quebec, Canada
This display piece is made up entirely of intersecting Elpidite sprays. Most of these sprays show some damage, but all are in reasonably good condition. The individual crystals reach lengths of up to 5" (12.7 cm) and are too intergrown for one to see a good example of their orthorhombic form. Their color ranges from brown to white and their luster from dull to pearly. There is no host rock of any sort on this piece.
no photo
elp-2 ($170.00)
Mount Saint-Hilaire, Quebec, Canada
 

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