The Mineral thorogummite
Thorogummite is always a replacement pseudomorph after Thorite, and is sometimes thought as being a variety of that mineral. However, Thorogummite is regarded by the IMA as a distinct mineral species with its own chemical formula. It forms when Thorite starts decaying from the radioactive metamiction process. When this happens, its crystal edges become rounded and smooth, and it eventually loses some silica (SiO4) molecules in its structure. The areas in the structure where the silica molecules were are replaced by hydroxyl (OH) molecules, and thus begins the transformation into Thorogummite.
Thorogummite is a highly radioactive mineral, and should be stored with all the precautions exercised with radioactive minerals.
Reddish-brown, greenish-brown, and yellowish-brown
Basic thorium silicate, with a varying amount of silica (SiO4) and hydroxyl (OH). The amount of hydroxyl present is dependent on how much silica is lacking. More hydroxyl means less silica.
Thorogummite may also contain some uranium partially replacing the thorium.
Color, luster, and strong radioactivity
In weathered rare earth granite pegmatites.
Thorogummite is an ore of the radioactive element thorium.
Thorogummite is found in localities containing Thorite where the Thorite has undergone metamiction. Localities includes Arendal, Langesundfjord, Norway; the Laach Lake Volcanic Complex, Eifel Mountains, Germany; the Bancroft District, Hastings Co., Ontario; the Thomas Range, Juab Co., Utah; the Seerie pegmatite, Jefferson Co., Colorado; and Barringer Hill, Llano Co., Texas.
Common Mineral Associations
Thorite, Quartz, Biotite, Orthoclase, Monazite, Xenotime, Betafite
Distingushing Similar Minerals
Carnotite and Tyuyamunite - Softer and lighter in weight.
Zircon and Hafnon - Harder, different streak.