Fluorite is calcium fluoride, CaF, a mineral mined and primarily used for flux in the making of steel. It is a soft mineral (Mohs' hardness of 4) that can be colorless, red, pink, orange, yellow, green, blue, purple, or nearly black. In the United States, major commercial depostits have been mined in the region of the Illinois-Kentucky border. Smaller deposits are widely scattered around the country. Fluorite has also been found in the southwestern part of New Hampshire, near Westmoreland. There, hot mineral-ladden water circulated through a system of fractures in the host rock and deposited quartz, barite, molybdenite, chalcopyrite, galena, and fluorite. This fluorite district consits of six or more veins that were commercially mined for fluorite for use as flux. The fluorite from some of these veins (especially the William Wise Mine) displays exceptional green color, clarity, and specimen forms. Because of the beautiful color and clarity, the Wise Mine (Privately owned and operated) has recently been reworked to recover green fluorite such as that show above.

Because fluorite is soft, and cleaves so readily, it is not suitable for jewelry purposes. In spite of this, collectors are drawn to its beautiful colors. Fluorite is not commonly faceted. It is difficult to obtain a brilliant polish on such soft material, and the resulting gems must be treated with great care to avoid damage. Nevertheless, museums and collectors search out and prize faceted fluorites to grace the shelves of their collections.