Category Pyrochlore group Space group Cubic 4/m 3* 2/m | Crystal system isometric Cleavage None | |
Formula(repeating unit) (Ca,U)2(Ti,Nb,Ta)2O6(OH) Color Amber yellow to dark brown | ||
Ellsworthite (Ca,U)2(Ti,Nb,Ta)2O6(OH) is a rare earth mineral mostly found in the northern parts of North America. It is named after H. V. Ellsworth of the Canadian Geological Survey by Walker and Parsons. Ellsworthite is also known under the name {Betafite}. It is a very U and Th rich mineral, which in fact makes it slightly radioactive. U makes up about 17.1% of the mineral.
Contents
Introduction
Ellsworthite is part of pyrochlore super group and the sub group betafite and was named after the Canadian Mineralogist and surveyor H. V. Ellsworth. Ellsworthite is also known as the mineral Betafite. Ellsworthite is a Th- bearing mineral that is found mostly in Canada and Alaska. It was first discovered in Hybla, Ontario, which is now a ghost town. Minerals of the pyrochlore group present one of the most important modes of occurrence of trace elements (Nb,Ta) and were found in various geological (geochemical) environments. It is very important geochemically that the pyrochlore structure is very suitable for diverse isomorphic substitutions.
Composition
Ellsworthite has complex hydrous oxides of Nb, Ta, Na, Ca, with hydroxyl and fluorine; it may contain as much as 17% U. It is composed of calcium, uranium, titanium, niobium, tantalum, and oxygen. Ellsworthite is heavily abundant in uranium, niobium and titanium oxides. It is very uranium, thorium, and water rich. One can consider Betafite as a hydrous uranium pyrochlore.
Structure
The structure of Ellsworthite is cubic and has a point group of 4/m 3* 2/m. It is part of the isometric system and has the space group Fd3m. It forms into a Hexoctahedral with {110}, {100}, {113}, {233}, and {230}. It has conchoidal fracture with no cleavage. Betafite is a synonym to Ellsworthite.
Physical Properties
Ellsworthite is mostly found in Canada and is amber yellow to dark brown in color. In most cases it has an amber rusty color and has a hardness of about 5.5. The luster is waxy or greasy to vitreous. The outer, more altered parts are relatively high in water and low in uranium. Its streak is yellow to brownish. The inner parts are brown, greenish brown, yellowish brown, or yellow. It is translucent to opaque