THE MINERAL FLUORRICHTERITE

Chemistry: Na2Ca(Mg, Fe)5Si8O22(OH, F)2, Sodium Calcium Magnesium Iron Silicate Hydroxide Fluoride.
Class: Silicates
Subclass: Inosilicates
Group: Amphibole
Uses: Only as mineral specimens.
Specimens

Fluorrichterite is a rare mineral, known from only one location. It is found near Wilberforce, Ontario in a skarn formation. The skarn is a term for a rock that is the product of a chemically unusual magma body that has intruded into and recrystallized a "dirty" limestone. The "dirty" limestone is not composed of just calcite, CaCO3, like "clean" limestone but is mixed with silicates and/or phosphates, etc. This mixing of the hot chemically unusual liquids and volatiles of the magma with the different minerals of the "dirty" limestones produces some interesting and rare minerals after all the recrystallizing is done. One of these is of course, fluorrichterite.

Fluorrichterite forms well shaped crystals that can have a pearly luster. Its luster is higher than most members of the amphibole group possibly because of the unusual presence of fluorine which comes from the unusual magma chemistry. Mixed with fluorrichterite in the white recrystallized calcite of the skarn are well formed crystals of biotite making specimens extra special.

Fluorrichterite is a brand new mineral, only receiving official recognition in 1996, although it has been collected for many years by many collectors. During this time specimens have been called various names in addition to fluorrichterite such as fluor-silicic-edenite, richterite (another amphibole mineral), augite (a pyroxene!) and many others. Its good to get this straightened out finally.

PHYSICAL CHARACTERISTICS:

Color is dark green to blue green or less commonly brown, gray and black.
Luster is vitreous to pearly to dull.
Transparency: Crystals are generally translucent to opaque.
Crystal System is Monoclinic; 2/m
Crystal Habits include prismatic crystals with an overall nearly diamond shaped cross-section with the four points usually cut by minor prism faces. The typical termination appears to be two faces of a slightly slanted dome but is actually two of the four faces of a prism. The termination faces are not only slanted toward each other but the two faces are slanted with respect to the long axis of the crystal as well. Some terminations are rather complex and can make the crystal appear pseudo-orthorhombic. Due to dissolution reactions after initial crystallization, the crystal faces can appear pitted and the terminations can be rounded. Twinning is commonly seen and results in a groove or notch running down the "spine" of the prismatic crystals.
Cleavage is imperfect in two directions at nearly 60 and 120 degrees.
Fracture is uneven.
Hardness is 6.
Specific Gravity is approximately 3 (average for translucent minerals)
Streak is white.
Other Characteristics: Crystals can have a iridescent shimer and associated minerals can be seen intergrown in some of the crystals filling pits and voids on their surface.
Associated Minerals are biotite, molybdenite, cancrinite and calcite
Notable Occurrence is several sites near Wilberforce, Ontario, Canada.
Best Field Indicators are locality, crystal habit (especially cross-section), color, pearly luster and cleavage.