While many Fluorite specimens glow under UV light, those from the Rogerley Mine are an extra special find because they change color in sunlight and artificial lighting. The colors change from a deep emerald green to bright cobalt blue. It is a fascinating phenomenon, and fluorite from this specific mine are highly praised in the mineral and gemstone community. This specific piece has wonderful glossy luster, great clarity, and clean, well preserved edges or terminations.
Measurements: ~5" long x 3-1/2" deep x 2" tall
Location: Helens Pocket, Lady Annabella Mine, Eastgate, Weardale, Durham Co., England
Fluorite is the "State Mineral" of Illinois. Fluorite forms in a variety of colors and is transparent to translucent in clarity. The chemical composition of Fluorite is CaF2, (calcium & fluorine.) The variation in colors are due to trace amounts of other elements replacing the calcium during the crystalline formation.
Fluorite is used in a variety of industrial purposes and the overwhelming percentage of Fluorite in the United States was mined in Illinois and Kentucky. Illinois became the leading Fluorite producer in the early 1940's, but during the 1990's, 90% of the U.S. Fluorite was imported with Illinois remaining the last U.S. producer.
Fluorite was was mined deep underground with many of the mines over 1,200 feet deep. The last Illinois mine was capped and flooded in 1995.
Unfortunately Covid is again on the rise, in Evanston.
Although not mandatory, masks are highly recommended.