THE MINERAL RHABDOPHANE

  • Chemistry: (Ce, La, Nd)PO4 - H2O, Hydrated Cerium Lanthanum Neodymium Phosphate.
  • Class: Phosphates
  • Group: Rhabdophane
  • Uses: As a minor ore of cerium and as mineral specimens.
  • Specimens

Rhabdophane is one of several rare earth phosphate minerals. Xenotime - (Y), monazite, churchite - (Y), florencite and belovite - (Ce) are a few of the more common ones. Although not very common, rhabdophane is common enough to be considered an ore of cerium. Rhabdophane is a mineral that forms from the alteration of rare earth igneous minerals and as a primary mineral in carbonatites and in a few rare hydrothermal veins. Its most noticeable feature is it greasy luster and botryoidal habit. Rhabdophane was named for its spectral signature which reveals the tell-tail spectral lines of its rare earth elements. Rhabdophane is basically Greek for "rods appearing".

Rhabdophane is actually a collection of three officially recognized minerals that are distinguished by their percentages of rare earth elements. Each is named for the rare earth element that composes the highest percentage of rare earth elements in that particular mineral. The three minerals are Rhabdophane - (Ce), Rhabdophane - (La), Rhabdophane - (Nd) All are very similar and difficult to distinguish. Most rhabdophane specimens are rhabdophane - (Ce) and this is most likely the mineral that is referred to when specimens are labeled simply as "rhabdophane".

Rhabdophane lends its name to a small group of phosphates. All members of the Rhabdophane Group are hexagonal or pseudo-hexagonal and have a general formula of (X)PO4 - 1-2H2O. The X can be either calcium, cerium, lead, lanthanum, neodymium, thorium, iron and uranium. Some sulfate ions, (SO4), can replace a portion of the phosphate ions, (PO4).

These are the members of the Rhabdophane Group:

  • Brockite (Hydrated Calcium Thorium Cerium Phosphate)
  • Grayite (Hydrated Thorium Lead Calcium Phosphate)
  • Ningyoite (Hydrated Uranium Calcium Cerium Phosphate)
  • Rhabdophane - (Ce) (Hydrated Cerium Lanthanum Phosphate)
  • Rhabdophane - (La) (Hydrated Lanthanum Cerium Phosphate)
  • Rhabdophane - (Nd) (Hydrated Neodymium Cerium Lanthanum Phosphate)
  • Tristramite (Hydrated Calcium Uranium Iron Phosphate Sulfate)

PHYSICAL CHARACTERISTICS:

  • Color is white, yellowish, pink to reddish brown.
  • Luster is greasy to dull.
  • Transparency: Specimens are translucent.
  • Crystal System is hexagonal; 6 2 2.
  • Crystal Habits include tiny hexagonal prisms but more commonly found as encrusting, massive, botryoidal and stalactitic formations.
  • Cleavage is absent.
  • Fracture is uneven.
  • Hardness is 3.5 - 4.
  • Specific Gravity is approximately 4.0 (above average for translucent minerals)
  • Streak is white.
  • Associated Minerals include limonite, serandite, amphiboles, natrolite, aegirine, astrophyllite, albite, calcite, biotite, rhodochrosite and rare earth granitic minerals.
  • Notable Occurrences include Majuba Hill, Pershing County, Nevada and Salisbury, Litchfield County, Connecticut, USA; Gakaia, Burundi: Fowey Consols, Cornwall, England; Grube Clara, Oberwolfach, Germany; Mt Weld, Western Australia; Kola Peninsula, Russia and Mont Saint-Hilaire, Quebec, Canada.
  • Best Field Indicators are crystal habit, color, luster and locality.
RHABDOPHANE specimens:
(hover for more info)
RHABDOPHANE specimen rha-1
$ 50.00
Dims: 1.2 x 0.4 x 0.3" (3.0 x 1.1 x 0.8 cm)
Wt: 6 g w/ base
Mount Saint Hilaire, Quebec, Canada
Two Rhabophane crystals make up the bulk of this thumbnail specimen. The larger of these is much larger than the other, measuring 1.2 x 0.3 x 0.2" (3.0 x 0.8 x 0.6 cm). Both are in excellent condition, showing no human-induced damage, and have indeterminate hexagonal form, taking on irregular, columnar habit. They have a common red-brown color and dull luster, and are hot-glued directly to the acrylic base, as there is no host rock present.
no photo
rha-1 ($ 50.00)
Mount Saint Hilaire, Quebec, Canada
RHABDOPHANE specimen rha-2
$ 150.00
Dims:1.5x1.2x1.0" (3.8x3.0x2.5 cm)
Wt: 1.1oz. (30g)w/base
Mt. St. Hilaire, Quebec, Canada
This specimen consists of several sheath-like bundles of rhabdophane crystals growing on and through large, well-formed analcime crystals. There is also a good crystal of serandite present on this specimen, as well as a tiny amount of an unidentified powdery-white mineral. The hexagonal form of this mineral cannot be ascertained from merely observing this specimen, however, this is an excellent example of this species. There is no damage to this specimen. It is firmly glued to a clear acrylic base.
no photo
rha-2 ($150.00)
Mt. St. Hilaire, Quebec, Canada
RHABDOPHANE specimen rha-3
$ 38.00
Dims: 1.1x0.7x0.9" (2.8x1.8x2.3 cm)
Wt: 0.4 oz. (11.3g)
Mt. St. Hilaire, Quebec, Canada
This thumbnail specimen is Rhabdophane-(La), as the rare earth is predominantly Lanthanum. This specimen includes at least 3 other minerals. The accompanying documentation reads "Rhabdophane-(La) and Dalyite", and I suspect that the dalyite is either the base (sprays of acicular colorless needles), or the cluster at one end (colorless parallel crystals that look more cubic than hexagonal to me), or the tiny crystals on top of that cluster (clearly hexagonal colorless transparent crystals). There is also some tiny perfect purple cubes (visible with a loupe) that look like fluorite. The Rhabdophane is several sprays of pale gray-green translucent acicular crystals perched on top of the specimen. These rare-earth specimens from Mount Saint Hilaire are often a hodge-podge of rare minerals.
no photo
rha-3 ($ 38.00)
Mt. St. Hilaire, Quebec, Canada
 

Copyright ©1995-2023 by Amethyst Galleries, Inc.