• Chemical Formula: (Ca, Na)2Nb2O6(O, OH, F); Calcium Sodium Niobium Oxide Hydroxide Fluoride.
  • Class: Oxides and Hydroxides
  • Group: Pyrochlore
  • Uses: A very minor ore of niobium and rare earth metals and as mineral specimens.
  • Specimens

Pyrochlore is one of the tantalum/niobium oxides that are generally difficult to distinguish. Fortunately there are few of them that form exquisitely shaped octahedral crystals. Pyrochlore crystallizes in the isometric symmetry class and forms fine octahedral crystals that are typically and characteristically modified by other isometric forms. Other members of pyrochlore's namesake group the Pyrochlore Group also form octahedrons, but can sometimes be reliably differentiated by color, streak and other characteristics.

Pyrochlore generally contains substantial amounts of radioactive elements called rare earths and this produces the radioactivity in this mineral. It is therefore a member of the informal group of minerals called the Rare Earth Oxides. These minerals are generally difficult to distinguish but the octahedral crystals of pyrochlore once again are usually sufficient indicators.

Pyrochlore is an end member of a solid-solution series between itself and the mineral microlite. The two minerals have similar structures and properties, but microlite is the tantalum rich end member and pyrochlore is the niobium rich end member. The generally lighter pyrochlore is found in a rather unusual igneous rock called a carbonatite (which is composed mostly of calcite) and alkalic pegmatites called nepheline syenites. The overall more common mineral microlite is found mostly in granitic pegmatite dikes and more rarely in the carbonatites. Pyrochlore is the more impure mineral of the two because it is more often accepting of the inclusion of elements such as tantalum, titanium, iron and uranium as well as the previously mentioned rare earth metals into its structure.

Some variety names of pyrochlore are known. "Hatchettolite" and "ellsworthite" both contain uranium and come from the same general location, albeit different mines, in the Hybla area of Hastings County, Ontario, Canada.

Remember, this is a radioactive mineral and should be stored away from other minerals that are subject to damage from radioactivity and of course human exposure should be limited !


  • Color is yellow, reddish-brown, red or black.
  • Luster can vary from vitreous, adamantine, greasy to resinous.
  • Transparency: Crystals are translucent with darker specimens being opaque.
  • Crystal System is isometric; 4/m bar 3 2/m
  • Crystal Habits typically include octahedral crystals that are modified by other isometric forms; also found cubic, granular as disseminated grains and massive.
  • Cleavage is in four directions (octahedral), but is indistinct.
  • Fracture is conchoidal to uneven.
  • Hardness is 5 - 5.5
  • Specific Gravity is approximately 3.5 - 4.6 (heavy for non-metallic). Variation caused by extent of inclusion of trace metals into the structure.
  • Streak is pale yellow to brown.
  • Other Characteristics: Generally radioactive.
  • Associated Minerals include calcite, feldspars, apatite, zircon and biotite.
  • Notable Occurrences include Veshnovorgorsk, Chelyabinsk Oblast, Russia; Mbeya, Tanzania; St. Peter's Dome, El Paso County, Colorado, USA; Brevik, Norway; Alno, Sweden; Oka, Quebec and Hastings County, Ontario, Canada.
  • Best Field Indicators are crystal habit, luster, fracture, color, hardness, radioactivity, associations, environment and specific gravity.
PYROCHLORE specimens:
(hover for more info)
PYROCHLORE specimen pyc-1
$ 30.00
Dims: 0.8 x 0.5 x 0.5" (2.0 x 1.3 x 1.3 cm)
Wt: 8.5 g w/ base
Oka, Quebec, Canada
At least one complete Pyrochlore crystal rests in the complex host rock of this small thumbnail specimen. The crystal is quite small, not exceeding 0.3" (8 mm) along any axis, but has somewhat warped but good octahedral form- its edges are well-defined and its faces are clean, possessing a slightly dull, submetallic luster. Its color is brownish-black and it is completely opaque in halogen light. The host rock in which it is embedded appears to be made up of compact, granular quartz with random pseudohexagonal biotite "books" that are in surprisingly good condition. The piece is hot-glued onto an acrylic base.
no photo
pyc-1 ($ 30.00)
Oka, Quebec, Canada
PYROCHLORE specimen pyc-2
$ 33.00
Dims: 0.9 x 0.6 x 0.6" (2.3 x 1.5 x 1.5 cm)
Wt: 12.0 g w/ base
Oka, Quebec, Canada
This small thumbnail specimen consists of two visible and complete Pyrochlore crystals that are partly embedded in a black-and-white granular host rock. The crystals have dimensions of 2 x 2 x 2 mm and 0.3 x 0.2 x 0.2" (8 x 5 x 5 mm), and are in excellent condition, showing no visible damage. Their octahedral form is very good, as they have well-defined edges and clean faces. Their color is black, their luster is submetallic, and they are both completely opaque. The surrounding host rock seems to be made up of granular quartz and well-formed pseudohexagonal "books" of biotite that were compacted into a rock of sorts. The piece is attached to an acrylic base with hot glue.
no photo
pyc-2 ($ 33.00)
Oka, Quebec, Canada
PYROCHLORE specimen pyc-3
$ 60.00
Dims: 0.8 x 0.7 x 0.7" (2.0 x 1.9 x 1.8 cm)
Wt: 5 g
Minas Gerais, Brazil
This thumbnail specimen consists of a single Pyrochlore octahedron. The crystal is in good condition. showing light damage on a few of its corners, and has good octahedral form, though some of its edges and surfaces are not quite even. The crystal has a dark brown color and a dull, matte luster and is not attached to any base or host rock.
no photo
pyc-3 ($ 60.00)
Minas Gerais, Brazil
PYROCHLORE specimen pyc-4
$ 60.00
Dims: 1.3x0.6x0.6" (3.4x1.6x1.5cm)
Wt: 0.43 oz. (12.3g)
Veshnovorgorsk, Chelyabinsk Oblast, Russia
This thumbnail has one large, nearly complete octahedral crystal of pyrochlore, along with several visible fragments of additional octahedrons, on a host rock of calcite and biotite. This specimen is only slightly radioactive, barely above background levels. The brownish-orange crystals are translucent and have many internal fractures which reflect orange highlights when the light hits them. The luster is vitreous, although the crystal surface is rather uneven (looking a lot like the surface of mica crystals).
no photo
pyc-4 ($ 60.00)
Veshnovorgorsk, Chelyabinsk Oblast, Russia
PYROCHLORE specimen pyc-5
$ 27.00
Dims: 1.3x0.9x0.9" (3.4x2.3x2.2cm)
Wt: 0.69 oz. (19.4g)
Vishnevogorsk, Ural, Russia
A single pyrochlore crystal rests in the white crystalline matrix of this specimen. The pyrochlore crystal is brown, somewhat distorted in shape (with two faces at 90 degrees), and has a wet vitreous luster. The crystal is dimply translucent, with a myriad of internal fractures. In direct sunlight, the fractures reflect yellow, orange, or even red highlights, depending upon their depth. There is also an abundance of black biotite crystals adding contrast to the host mineral.
no photo
pyc-5 ($ 27.00)
Vishnevogorsk, Ural, Russia
PYROCHLORE specimen pyc-6
$ 25.00
Dims: 0.99x0.94x0.89" (2.50x2.38x2.27cm)
Wt: 0.57oz (16.3g)
Vishnevogorsk, Ural, Russia
Dozens of nice crystals of pyrochlore adorn all sides of this specimen. They look quite a bit like some garnets, with a bright luster, brown color, and orange highlights from internal reflections (revealing translucency). And while some of the crystals have a complex, garnet-like shape, others are clearly cubic or octahedral. Careful examination suggests that even the garnet-like chapes are really octahedrons with all corners flattened, resulting in a crystal with 14 sides. The off-white host rock looks like a white, translucent feldspar, judging by areas of cleavage.
no photo
pyc-6 ($ 25.00)
Vishnevogorsk, Ural, Russia
PYROCHLORE specimen pyc-7
$ 25.00
Dims: 1.20x1.08x1.01" (3.05x2.75x2.57cm)
Wt: 0.93oz (26.5g)
Vishnevogorsk, Ural, Russia
Most of the pyrochlore crystals on this specimen are damaged, but that just reveals the color and transparency of the thinner sections. The pyrochlore is brown with orange highlights, and has a vitreous luster. The host rock appears to be composed of both calcite and a feldspar of some kind, with hundreds of tiny pyrochlore crystals included.
no photo
pyc-7 ($ 25.00)
Vishnevogorsk, Ural, Russia


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