Thorite variety "orangite" from Franklin, NJ
Above photo taken at 30x magnification
Thorite{ThSiO4}: variety "orangite" - red-orange to rust-brown, tiny crystals, grains, and masses
Altered thorite (thorogummite?) - yellow to orange coatings.
Thorutite : gray to black; resinous or glassy luster.


John Cianciulli really loved the minerals of Franklin and Sterling Hill, and it showed. You could bring your mineral finds into John's office, and he'd always spend the time to help you identify them. He was really good at sight identification when it came to Franklin and Sterling Hill minerals. (John seemed to have a friendly competition going on with the Mont-Sainte Hilaire crowd, to see which locality would end up with biggest variety of mineral species. Only mineral enthusiasts seem to appreciate how enjoyable such a pursuit can be, but trust me, it's a lot of fun.)

One day I was talking with John, and he showed me a mineral that Jim Rumrill had found on the Buckwheat Dump. Analysis had shown it to be thorutite, newly-discovered for the locality. John showed me the assemblage in which it occurred, and pretty soon I was down on the Buckwheat looking for this assemblage with a loupe and a Geiger counter.

Eventually I found a couple pieces of dolomite having the characteristic appearance of the thorutite assemblage. Now mind you, this isn't typical dolomite rock. It's material that seems to have formed right on the edge of the "pegmatite" zones, so there are a few minerals in it that you don't normally find in the Buckwheat dolomite.

Note: While thorite is pretty strongly radioactive as minerals go, what you find on the dump occurs in such small amounts that it's only faintly radioactive... so weak that you need to put the G-M tube almost right up to the rock to get noticeable clicks above background. So before you freak out that there are radioactive minerals on the Buckwheat Dump, the levels of radioactivity are extremely small. To put things in perspective, the Buckwheat rocks as a whole are among the least radioactive of all the northern New Jersey rocks that I've encountered. Franklin was a zinc mine, not a uranium mine.

Thorite and other minerals, shown at 30x magnification
Above photo taken at 30x magnification. The dark, red-brown, distorted crystal toward the bottom of the photo is thorite, along with the tiny red spots around it. The thorite crystal is about 1/4 millimeter across.
The larger, dark mass above it is most likely thorutite.
The region shown in the photo is from the most radioactive section of the specimen.

So I went back to John's office and showed him the unusual-looking dolomite chunks I'd found. He examined them with the microscope and said this was indeed the thorutite assemblage. He said the orange mineral is thorite, specifically the variety once known as "orangite". The surrounding minerals, he told me, are altered thorite and possibly some massive thorutite. There is also what appears to be altered lennilenapeite or clinochlore in the specimen, plus some ordinary goethite or "limonite". Of course, there's also quartz, dolomite,a mica that appears to be biotite, and a couple of unidentified accessory minerals.

Photo taken at 10x magnification
The "mess" shown above contains thorite, thorutite, their alteration products, dolomite, iron oxides, and who-knows-what-else. It is a jumble of minerals. The thorite and thorutite shown in the previous photo are part of this region, where much of the specimen's radioactivity is concentrated.



Photo index




Site content and photos are copyright 2008-2009, njminerals.org