THE MINERAL PYROPE

  • Chemistry: Mg3Al2(SiO4)3, Magnesium Aluminum Silicate
  • Class: Silicates
  • Subclass: Nesosilicates
  • Group: Garnets
  • Uses: Gemstone and abrasive
  • Specimens

Pyrope is the only garnet that is always a shade of red. Although less common than most other garnets, pyrope is a common gemstone.

Pyrope is the only garnet whose most common source is igneous rather than metamorphic. Most pyrope comes from ultramafic igneous rocks that contain olivine and/or diamond. Metamorphic pyrope comes from the metamorphism of the igneous rocks previously mentioned or from magnesium rich rocks subjected to high grade metamorphism.

Almandine and pyrope form a series in which iron substitutes for the magnesium in pyrope. In fact, pure pyrope is unknown in nature and the various proportions are referred to as pyrope-almandine mixes.

One mixture of approximately two to one (pyrope to almandine) is a variety called rhodolite which has an attractive red-lavender color and is cut as a gemstone. Pyrope is difficult to distinguish from almandine but is usually clear and free from flaws, at least more so than almandine.

PHYSICAL CHARACTERISTICS:

  • Color is red to reddish purple and sometimes a deep enough red to appear black.
  • Luster is vitreous.
  • Transparency crystals are transparent to translucent.
  • Crystal System is isometric; 4/m bar 3 2/m
  • Crystal Habits include the typical rhombic dodecahedron. also seen is the 24 sided trapezohedron. Combinations of these forms are common and sometimes the rare faces of the hexoctahedron, a 48 sided crystal habit that rarely is seen by itself, can also combine with these other forms making very attractive, complex and multifaceted crystals. Massive and granular occurrences are also common.
  • Cleavage is absent.
  • Fracture is conchoidal.
  • Hardness is 7 - 7.5
  • Specific Gravity is approximately 3.6 (above average for translucent minerals)
  • Streak is white.
  • Associated Minerals are olivine, serpentine, biotite, hornblende, augite, pyroxenes and diamond.
  • Other Characteristics: index of refraction is 1.73
  • Notable Occurrences include localities in Europe; Arizona and New Mexico, USA; South Africa and several Australian sites.
  • Best Field Indicators are crystal habit, color, hardness and enviroment.
PYROPE specimens:
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PYROPE specimen pyo-2
$ 250.00
Dims:3.4x2.8x0.7" (8.6x7.1x1.8 cm)
Wt: 5.4oz. (153g)
N'Chwanning Mine, Kuruman, S. Africa
This is one of the best cabinet-sized specimens of pyrope garnet that I have ever seen. A rich crust of dodecahedral crystals covers this specimen. These crystals grow to 0.1" (0.3cm) in size, and, when held up to a bright light and examined with a loupe, are faintly translucent. The back of the specimen is also covered with pyrope crystals, although these are very tiny. Good crystals of pyrope are very difficult to find, and this is a wonderful specimen.
no photo
pyo-2 ($250.00)
N'Chwanning Mine, Kuruman, S. Africa
PYROPE specimen pyo-1
$ 48.00
Dims:1.9x0.9x0.7" (4.8x2.3x1.8 cm)
Wt: 1.6oz. (43g)
Almklov, Norway
This specimen consists of several shattered pyrope garnet crystals in an olivene matrix. These crystals range in size from tiny to 0.2" (0.5cm). The largest crystal shows good conchoidal fracture on one surface. All of the crystals are too damaged to identify the characteristic isometric form.
no photo
pyo-1 ($ 48.00)
Almklov, Norway
PYROPE specimen pyo-3
$ 125.00
Dims: 4.2x3.7x3.0" (10.6x9.3x7.6 cm)
Wt: 54.5 oz. (1.54kg)
San Valerio, Tocantins, Brazil
This is a pair of huge rhodolite garnets. Possibly it started as a single large crystal which broke and healed, or perhaps it is two rhodolite garnets that grew together. I suspect that it is one garnet that split, based upon the size similarity and that the crystal faces are roughly aligned. In any case, this appears as a nodule with two halves. The halves are slightly concave - they do not meet in the center, only around the edges. Also, while it is easy to count the 12 faces of the pair, these crystals appear rather distorted and weathered, with deep fissures all over the surface. The crystals have a deep burgandy color, and the thin sections along the fissures are transparent. The crystals have a good luster, with the thousands of crystal points all reflecting at once. The only human damage is apparent as dark, vitreous fractures revealing the true internal color of the specimen.
no photo
pyo-3 ($125.00)
San Valerio, Tocantins, Brazil
PYROPE specimen pyo-4
$ 25.00
Dims: 2.7x1.6x1.5" (6.9x4.1x3.9cm)
Wt: 7.1oz. (202g)
Minas Gerias, Brazil
This is two red pyrope garnet crystals in a small amount of silvery mica schist. The garnet crystals are rather warped in shape (the smaller was broken, apparently before the mica overgrowth). The largest crystal measures 4.2cm along its largest visible dimension.
no photo
pyo-4 ($ 25.00)
Minas Gerias, Brazil

 


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