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.