THE MINERAL TARBUTTITE

  • Chemistry: Zn2(PO4)(OH), Zinc Phosphate Hydroxide.
  • Class: Phosphates
  • Uses: only as a mineral specimen.
  • Specimens

Tarbuttite is a somewhat rare phosphate mineral but is popular among collectors of rare minerals, especially rare phosphates. It forms good crystals and has a nice luster. Occasionally, the colors can be rather attractive although they are commonly pale. It is usually associated with the colorful limonite, an iron oxide, and the combination can make for a nice cabinet specimen.

Tarbuttite is named after Percy Coventry Tarbutt, a Director of the Broken Hill Exploration Company who collected specimens at the type locality of Broken Hill, Zambia.

PHYSICAL CHARACTERISTICS:

  • Color is colorless and pale white, red, green, yellow or brown.
  • Luster is vitreous.
  • Transparency crystals are transparent to translucent.
  • Crystal System is triclinic, bar 1
  • Crystal Habits include deeply striated prismatic crystals or crusts.
  • Cleavage is perfect in one direction.
  • Hardness is 3.5 - 3.7
  • Specific Gravity is approximately 4.2 (heavy for translucent minerals)
  • Streak is white.
  • Associated Minerals are limonite, smithsonite and some other oxidized zinc ore deposit minerals.
  • Notable Occurrences include Broken Hill (now Kabwe), Shaba, Zambia and elsewhere.
  • Best Field Indicators are crystal habit, locality, associations with other zinc ores and/or phosphate minerals and density.
TARBUTTITE specimens:
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TARBUTTITE specimen tar-1
$ 235.00
Dims: 2.1" x 2.0" x 1.2" (5.3 x 5.1 x 3.0 cm)
Wt: 2.82 oz. (80.2 g)
#2 Open Pit, Broken Hill Mine, Kabwe, Zambia
Though not very colorful, the Tarbuttite crystals that line the crevice in this dull limonite host rock have excellent form, and a rather interesting one, at that. They are small, not exceeding 0.3" (8 mm) in any dimension, and show a dull pearly luster. Oddly, the two main faces on these tabular crystals seem to be coated with a thin, milky layer of the material, whereas their thinner faces are clear. Thus, they are transparent and moderately clear when viewed from all directions except two. Their triclinic form is excellent, and only the most exposed crystals show any damage. They appear to be nearly rhombohedral in form, and are easy to see against the dull red-brown color of their limonite host.
no photo
tar-1 ($235.00)
#2 Open Pit, Broken Hill Mine, Kabwe, Zambia
TARBUTTITE specimen tar-2
$ 125.00
Dims: 2.4" x 1.9" x 1.5" (6.1 x 4.8 x 3.8 cm)
Wt: 3.2 oz. (91.1 g)
Broken Hill Mine, Kabwe, Zambia
Scores of tiny Tarbuttite crystals rest on the base of stalactitic goethite of this specimen. These crystals are quite small, not measuring more than 0.2" in length, but are generally in good condition, though one tight cluster is obviously heavily damaged. All show good triclinic tabular form, with well-defined edges and clean faces that possess a rather dull pearly luster. All have a pale cream-coloration that is very subtly rust-stained due to their association with the iron oxide base rock, and are dimly transparent. Most of these are intergrown into clusters of 1 to5 crystals, and close examination will reveal that many are wedged into small recesses that extend deep into the goethite. The goehtite itself shows substantial damage, but cons
no photo
tar-2 ($125.00)
Broken Hill Mine, Kabwe, Zambia
TARBUTTITE specimen tar-3
$ 25.00
Dims: 2.8 x 1.7 x 1.3" (7.0 x 4.4 x 3.4 cm)
Wt: 3.7 oz. (104 g)
Broken Hill Mine, Kabwe, Zambia
Several clusters of warped, intergrown Tarbuttite crystals rest on the goethite/limonite base of this hand specimen. These crystals do not exceed 0.3" (8 mm) in length and are generally in good condition, as several of the smaller ones are damaged. Their triclinic form is somewhat warped due to intergrowth and possible growing conditions, but is still discernable. They are generally colorless, transparent and dimly to moderately clear, though each seems to have a faint red-brown tint from the limonite. Their luster ranges from a bright pearly to waxy.
no photo
tar-3 ($ 25.00)
Broken Hill Mine, Kabwe, Zambia
TARBUTTITE specimen tar-4
$ 70.00
Dims: 2.6x1.4x1.7" (6.5x3.6x4.2 cm)
Wt: 3.0 oz. (86.3g)
Broken Hill Mine, Kabwe, Zambia
When I purchased this specime, I thought that the tarbuttite was the scattering of milky crystals and that the clear ones were calcite. I was wrong - with a loupe, I could see that the clear ones are tarbuttite, also, and these are excellent crystals. They are relatively small (a millimeter or two), and they have perfect tabular form, looking like flattened colorless fluorite crystals. This tarbuttite "druze" covers much of the limonite base, so there is a lot of the mineral on this specimen.
no photo
tar-4 ($ 70.00)
Broken Hill Mine, Kabwe, Zambia
TARBUTTITE specimen tar-5
$ 40.00
Dims: 2.49x1.97x1.28" (6.32x5.00x3.25cm)
Wt: 3.42oz (96.8g)
Broken Hill Mine, Kabwe, Sambia
This specimen is largely covered with a druze of tiny prismatic tarbuttite crystals. These are colorless, and show excellent luster and form. There are other minerals present - the host rock is composed of limonite and possibly goethite, and there are scattered radial sprays of find milky crystals which I have not identified.
no photo
tar-5 ($ 40.00)
Broken Hill Mine, Kabwe, Sambia
TARBUTTITE specimen tar-6
$ 30.00
Dims: 0.91x0.87x0.77" (2.31x2.21x1.97cm)
Wt: 0.25oz (7.2g)
Broken Hill, Zambia
The sparkle on this specimen all comes from colorless transparent vitreous crystals of tarbuttite. Their small prismatic crystals rest on a matrix of several other minerals, possibly including goethite and some light brown mineral.
no photo
tar-6 ($ 30.00)
Broken Hill, Zambia
 

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