There’s a new exhibit at the National Museum of Natural History featuring items to represent each of the U.S. states and territories. The Granite State is represented by a rock.
No, not that type of rock. It’s fluorite, a bright green sample of calcium fluoride taken from the William Wise mine in Westmoreland, west of Keene.
The gorgeous mineral sample is one of roughly 600 items taken from the museum’s massive collection for the exhibit, called “From These Lands: Sharing Our Natural and Cultural Heritage.” It includes fossils, plants, animals and human-made objects.
Along with fluorite, New Hampshire is represented by two flying insects: a moth with the great name of modest sphinx and the less-exciting tachinid fly. Our neighbors get more interesting items: Vermont has marble quarried from Barre and Maine gets lobsters and Atlantic sturgeon. You’d think at least we could have Karner blue butterflies or maple syrup.
Anyway, I had never heard of fluorite before this, so I asked Shane Csiki, the state geologist, for some guidance. Here’s what I’ve learned.
Fluorite can occur in a variety of colors, depending on the geologic process that made it. The Westmoreland deposit, I read in one of several mineral-collecting websites, came about when hot mineral-laden water circulated through a system of fractures in the host rock and deposited stuff like quartz, barite and molybdenite.
Fluorite is a soft mineral that can’t be polished or cut into facets, so it is useless for jewelry or other decoration despite its color. Its main commercial value was as flux, the material that helps remove impurities when making steel.
The Westmoreland vein has been known about since at least the 1840s. A pit mine operated from about 1908 to 1917 and is reported to have produced approximately 3,500 tons of fluorspar, according to an official report issued in 1946. It passed through the hands of a couple of companies, including the American Steel & Wire Co., and in World War II the federal Bureau of Mines studied it as a potential source of fluorite, but apparently nothing came of that.
The mine is now privately owned, and it’s hard to know if any fluorite is being taken out. You can find plenty of pretty green samples for sale online, if you’re so interested.
For me, the main point of interest here is that even in a geologically unexciting place like New Hampshire, which lacks volcanoes, earthquake faults, petrochemical deposits or hot springs, interesting minerals lurk underground.
