THE MINERAL LEGRANDITE

  • Chemistry: Zn2AsO4(OH) - H2O, Hydrated Zinc Arsenate Hydroxide
  • Class: Phosphate Class
  • Subclass: Arsenates
  • Uses: Only as mineral specimens
  • Specimens
Legrandite is a rare and beautiful mineral that is a favorite of mineral collectors. It is known world wide from the famous localities around Mapimi, Mexico. Legrandite is a vitreous mineral that seems to radiate its unusually rich yellow color. No other mineral is associated with limonite that has a bright yellow color with prismatic crystals and therefore legrandite is pretty easy to identify. However it is rare and not so easy to find. Good specimens are hoarded by the collectors who are lucky enough to find them.

PHYSICAL CHARACTERISTICS:

  • Color is straw to orange yellow to colorless.
  • Luster is vitreous.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include prismatic to bladed crystals with a wedge shaped termination often complexly faceted.
  • Cleavage is poor in one direction.
  • Fracture is uneven.
  • Hardness is 4.5 - 5.
  • Specific Gravity is approximately 4.0 (above average for translucent minerals)
  • Streak is white.
  • Associated Minerals are adamite, limonite, pyrite, sphalerite, smithsonite, austinite, paradamite, aragonite, calcite, mimetite and other oxidation zone minerals.
  • Notable Occurrences include the famous mines at Mapimi, Mexico as well as Flor de Pena Mine, Mexico.
  • Best Field Indicators are color, luster, density, associations and crystal habits.
LEGRANDITE specimens:
(hover for more info)
LEGRANDITE specimen leg-1
$ 144.00
Dims: 2.9 x 1.6 x 1.2" (7.4 x 4.1 x 3.1 cm)
Wt: 3.1 oz. (88 g)
Ojuela Mine, Mapimi, Durango, Mexico
A single Legrandite aggregate rests in a hollow in the calcareous host of this hand specimen. The aggregate has visible dimensions of 0.6 x 0.5 x 0.3" (1.5 x 1.2 x 0.7 cm) and is in excellent condition due to its protective surroundings. Due to intense intergrowth, it is impossible to isolate individual crystals, but their crystalline tendencies are obvious. All have a rather deep yellow color and a pearly-to-vitreous luster, and are translucent. The hollow in which they rest is lined with bright-red, powdery limonite, and a few tiny, white crystals rest nearby- they could be either aragonites or austinites, I am not sure which.
no photo
leg-1 ($144.00)
Ojuela Mine, Mapimi, Durango, Mexico
LEGRANDITE specimen leg-2
$ 84.00
Dims: 2.8 x 2.4 x 1.8" (7.2 x 6.0 x 4.7 cm)
Wt: 9.3 oz. (264 g)
Ojuela Mine, Mapimi, Durango, Mexico
The calcareous base of this small cabinet specimen holds several sheaf-like Legrandite aggregates. These aggregates do not exceed 0.4" (1 cm) in length and are generally in very good condition, due to the protective nature of the host rock. All show a rather well-defined, thin monoclinic prismatic form, the standard deep-yellow color and a bright pearly luster. Though individual crystals are transparent, the aggregates are merely translucent. A crust of creamy, often rust-stained calcite or dolomite coats the limestone base beneath the Legrandites.
no photo
leg-2 ($ 84.00)
Ojuela Mine, Mapimi, Durango, Mexico
LEGRANDITE specimen leg-3
$ 48.00
Dims: 2.0 x 1.4 x 1.4" (5.0 x 3.6 x 3.5 cm)
Wt: 2.9 oz. (83 g)
Ojuela Mine, Mapimi, Durango, Mexico
A compact cluster of nearly parallel Legrandite crystals rests on the limonite base of this hand specimen. These needles appear to be in good condition and reach lengths of nearly 0.5" (1.2 cm). Their yellow color and bright pearly-to-vitreous luster are standard for their specie, and though they appear to be transparent, they are generally too intergrown for this trait to show. This intergrowth also makes it difficult to study their monoclinic form. The limonite base on which they rest is partly covered with crusts of what appear to be calcite.
no photo
leg-3 ($ 48.00)
Ojuela Mine, Mapimi, Durango, Mexico
 

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