Tyrrellite
Encyclopedia
Tyrrellite is a selenide mineral
that has a formula of Cu(Co,Ni)2Se4. It has been found in the Goldfields District in northern Saskatchewan
, as well as in the Petrovice deposit, Czech Republic
. It is named after the Canadian geologist Joseph Burr Tyrrell. Joseph Tyrrell was one of the first geologists from the Geological Survey of Canada to do research in the Goldfields District.
, meaning that crystallographically, it has three axes of equal length perpendicular to one another. It belongs to the space group, Fd3m. Because tyrrellite is isometric, it is also isotropic. Isotropic minerals are defined as follows: when light passes through an isometric mineral, the light moves in all directions with equal velocity. In contrast, for anisotropic minerals, the velocity of light passing through the mineral varies with crystallographic direction. Tyrrellite displays a light bronze color when viewed in plane polarized light. Because tyrrellite is isotropic, the light bronze color will remain constant as the mineral is rotated and viewed from different crystallographic angles. When viewed under cross polarized light, tyrrellite displays total extinction, a characteristic trait of isotropic minerals.
, a primary mineral of deposits in which tyrellite is found. The relative scarcity and unique occurrences of tyrrellite can give geologists considerable insight into the circumstances under which the parent rock formed.
Selenide mineral
Selenide minerals are those minerals that have the selenide anion as a main component.Selenides are similar to sulfides and often grouped with them.Examples include:* athabascaite Cu5Se4* clausthalite PbSe* penroseite Se2* stilleite ZnSe...
that has a formula of Cu(Co,Ni)2Se4. It has been found in the Goldfields District in northern Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
, as well as in the Petrovice deposit, Czech Republic
Czech Republic
The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....
. It is named after the Canadian geologist Joseph Burr Tyrrell. Joseph Tyrrell was one of the first geologists from the Geological Survey of Canada to do research in the Goldfields District.
Crystallography
Tyrrellite is isometricCubic crystal system
In crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals....
, meaning that crystallographically, it has three axes of equal length perpendicular to one another. It belongs to the space group, Fd3m. Because tyrrellite is isometric, it is also isotropic. Isotropic minerals are defined as follows: when light passes through an isometric mineral, the light moves in all directions with equal velocity. In contrast, for anisotropic minerals, the velocity of light passing through the mineral varies with crystallographic direction. Tyrrellite displays a light bronze color when viewed in plane polarized light. Because tyrrellite is isotropic, the light bronze color will remain constant as the mineral is rotated and viewed from different crystallographic angles. When viewed under cross polarized light, tyrrellite displays total extinction, a characteristic trait of isotropic minerals.
Discovery and occurrence
It was first described in 1953 for an occurrence in the Goldfields District, Saskatchewan, while the second occurrence was reported in Petrovice deposit, Czech Republic. In general, tyrrellite is veined, embayed and replaced by umangiteUmangite
Umangite is a copper selenide mineral, Cu3Se2, discovered in 1891. It occurs only in small grains or fine granular aggregates with other copper minerals of the sulfide group. It has a hardness of 3. It is blue-black to red-violet in color with a black streak. It has a metallic luster.Umangite is...
, a primary mineral of deposits in which tyrellite is found. The relative scarcity and unique occurrences of tyrrellite can give geologists considerable insight into the circumstances under which the parent rock formed.