 Curtisite
This is a small cabinet specimen of curtisite on sandstone from the mercury mine at Skagg's Springs, near Healdsburg, Sonoma County, California. Ex: Curt G. Segeler Collection - collected in December 1947. The tag has C24H18 as the formula. Curtisite was originally applied to a mineral described in 1926, which in 1975 was determined to be a mixture of hydrocarbons. Now it's considered a variety of idrialite (yellowish-green under LUV). This specimen, however, glows a bright mint-green under LUV. The formula matches that of p-quaterphenyl, a highly fluorescent chemical used in scintillators. The latest analyses of curtisite (and idrialite) show them to be complex mixtures of polycyclic aromatic hydrocarbons. Thanks to Val Collin's auction on eBay for the specimen! |
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 Gilsonite
Gilsonite's a natural hydrocarbon resin (asphalt) - this small cabinet piece of very pure "select grade" is from the type (and only) locality of the Uintah valley, Uintah County, Utah. It's named after Samuel H. Gilson who
was the first to promote it and mine it commercially in the 1880s, after discovering that it can be used as waterproofing and wire insulation. His company, Gilsonite Manufacturing, founded in 1888, is still in existence today. The source of the gilsonite is believed to be kerogen in the Green River formation deep below the Uintah basin in eastern Utah. Thermal reduction and pressure, over time, created the deposits. It's also called uintahite, after the type locality. Thanks to Jan Garland's (Fine Rocks) auction on eBay for the specimen and the images! | |
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 Humboldtine
Humboldtine (humboldtite) is dihydrated ferrous (iron) oxalate and it occurs here as rusty patches on an epidote matrix. This large miniature comes from Salida, Chaffee County, Colorado. It's the iron analog of weddellite (calcium) and glushinskite (magnesium). Thanks to Thomas Bee's auction on eBay for the specimen and the image! |
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 Karpatite
Karpatite (carpathite, pendletonite) or coronene, as it's known synthetically, is a fused group of six benxene rings. It occurs here on this specimen from the 4th of July Mine, near Picacho Peak, San Benito County, California, as radial light yellow sprays on matrix. They are, like a lot of cyclic organic compounds, highly fluorescent (bright bluish-white, larger image). Thanks to Tony Nikischer at the Excalibur Mineral Company for the specimen! |
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 Siegburgite
Tiny orange grains of siegburgite, a naturally occuring (fossil) polystyrene resin, in sandstone [miniature] from the type locality of Siegburg, Nordrhein-Westfalen, Germany. It has a 1920 - 1930 tag. Thanks to Thomas Bee's auction on eBay for the specimen and the image! | |
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 Whewellite
A thumbnail aggregate of whewellite (calcium oxalate) crystals from Hartenstein, Saxony, Germany, Thanks to C. Carter Rich's table at the 2003 Carnegie Gem & Mineral Show for the specimen! |
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