Charlesite is a sulfate mineral of the ettringite group. Charlesite was named in 1945 after Dr. Charles Palache, a mineralogist and professor at Harvard University for his work on minerals. This mineral is extremely rare, and when it is found it is usually in crystal (but not gem) form. Its crystals are soft and hexagonal, and can vary in color.http://rruff.info/doclib/am/vol68/AM68_1033.pdf Handbook of Mineralogy Colors can range from clear to white, or even pale yellow or pink. The brittle mineral's Mohs hardness is 2.5 with a specific gravity of 1.79. Though transparent to the eye, the mineral has a white streak.http://webmineral.com/data/Charlesite.shtml#.Vl9UQuk0_wx WebMineral.com

Occurrence

Charlesite has only been found in a few specific locations in the world. The first was its place of discovery at Franklin Mine in Franklin, Sussex County, New Jersey. It was located immediately above the 800 level, about 15 feet into the ore from the hanging wall. The ore mostly consisted of franklinite and willemite and several other minor minerals. The crystals found at this location were up to 6mm in length and were suspected to have grown alongside clinohedrite crystals.http://rruff.info/doclib/am/vol68/AM68_1033.pdf Handbook of Mineralogy

The other location where charlesite has been located is the Wessel's Mine, N' Chwaning Mines, and Kalahari Manganese Fields in Northern Cape Province, South Africa. The Wessel's Mine is thought to be the only source for charlesite to be found in gem quality.http://classicgems.net/gem_charlesite.htm ClassicGems.net

Several other recorded places are Germany, Japan, Norway, Romania, and Slovakia.http://www.mindat.org/min-971.html MinDat.Org

Uses

Due to its rarity, there are very few uses for charlesite. Though there is not much of the mineral, one of the major uses for specimens that meet the necessary standards is gems. Due to its softness, it will not be found in much jewelry.http://rruff.info/doclib/am/vol68/AM68_1033.pdf Handbook of Mineralogy

Some other uses could be for studying the reasons for the rarity of the mineral, teaching mineralogy classes, or even serving as items for collectors or museums of rare minerals.

Composition

Element Percent Header Calcium 19.48% Ca Aluminum 3.28% Al Silicon 1.14% Si Boron .88% B Hydrogen 5.23% H Sulfur 5.20% S Oxygen 64.81% O

Oxides Percent CaO 27.26% Al2O3 6.19% SiO2 2.43% B2O3 2.82% H2O 46.7% SO3 12.97%

http://webmineral.com/data/Charlesite.shtml#.Vl9UQuk0_wx WebMineral.com

References

Dunn P.J., Peacor D.R., Leavens P.B., Baum J.L.,1983, American Mineralogist, Charlesite, a new mineral of the ettringite group, New Jersey http://rruff.info/doclib/am/vol68/AM68_1033.pdf Handbook of Mineralogy