9 January 2015
To a novice like me, this rock is interesting because of its shape and color, but I would never have found its photo if it hadn’t had pizzazz.
It’s a rare and valuable specimen of Willemite, Franklinite and Rhodonite. Mineralogists can tell you that Franklinite pinpoints its origin right down to a single county — Sussex County, New Jersey — the only place on earth where Franklinite is found. This rock came from the Sterling Mine at Ogdensburg.
But that’s not what I mean about pizzazz.
Back in October at the Wissahickon Nature Club we learned about fluorescent minerals from Harlan Clare who showed us many samples under normal and “black” light. What really impressed me is that a boring rock can display amazing colors if the mineral is fluorescent.
Expose this rock to ultraviolet light and it bursts into glowing green and orange!
Most rocks look boring in normal light so how did people figure out that some of them glow?
At a rock mine the ore sits out in the sun for a while after it’s pulled from underground. If you take a fluorescent rock back into the dark mine, it glows because it was exposed to the sun’s ultraviolet light. Sir George Gabriel Stokes named this fluorescence in 1852 when he described why fluorite glows.
So now when you see a basket of boring rocks for sale, think of the possibilities. When you know what you’re looking at you can find one with a hidden punch. Harlan Clare carries a small UV flashlight so he can preview the rocks before he buys.
Some rocks are like willets. They are boring until they open their wings.
(Two photos of Willemite, Franklinite, Rhodonite from the Sterling Mine, Sterling Hill, Ogdensburg, New Jersey (George Elling Collection) by Rob Lavinsky, iRocks.com – CC-BY-SA-3.0, via Wikimedia Commons. Click on the images to see the originals)
Harlan Clare had the most interesting show and tell. We were all oohing and aahing like little kids when he turned the black light on his samples. Nature never ceases to surprise.
A visit to the Sterling Hill Mining Museum is definitely recommended for anyone who likes rocks. You can get a tour of the old mine, and can search through the old mine dump for rock specimens to take home. There is a building where there are black lights available so that you can see how well the rocks you found fluoresce before you decide to buy them. I have some rocks from the mine that were polished for use in jewelry. It’s a great place to visit if you’re in Northern New Jersey.
Sorry I missed the program. Thanks for the info about the Sterling Hill Mining Museum. Yeah, rocks are cool and many have a tremendous economic value.