Formula
(repeating unit) Ca2Mg5 (Si8O22) (OH)2 Twinning simple, multiple | Space group monoclinic – prismatic | |
Category mineral variety of tremolite Color red to pink, lilac to purple Crystal habit elongated, bladed crystals, granula | ||
Hexagonite is the red to pink, lilac to purple manganoan variety of tremolite. A rare amphibole, it can be transparent, translucent, and rarely opaque.
Contents
Properties
Hexagonite is pleochroic, potentially displaying varying shades of blue, violet, purple, or red. It is also known as "mangan-tremolite", since the manganese imparts the mineral's unique colors. Pink, lilac, and purple are the most common colors. Transparent examples with nice coloration are most prized. Hexagonite can also display a good Cat's eye effect. Hexagonite has been successfully faceted.
Chemical formulae and history
Tremolite was discovered in 1789. Hexagonite, a varietal form of tremolite, has a Mohs hardness of 5.0-6.0. Like tremolite, it is a calcium magnesium silicate hydroxide with the formula: Ca2Mg5 (Si8O22) (OH)2.
The mineral was given the name, hexagonite, because its crystal structure was believed at one time to be hexagonal. Since then, however, it has been found to be monoclinic.
Found
Today, the mineral is found primarily in the Balmat-Edwards zinc district of St. Lawrence County, New York, United States. Although very rare, it can be found elsewhere in other locations worldwide.