Macdonaldite
Encyclopedia
Macdonaldite is a rare barium
silicate mineral with a chemical formula of BaCa4Si16O36(OH)2·10H2O. Macdonaldite was first described in 1965 and named for Gordon Andrew Macdonald (1911-1978) an American volcanologist at the University of Hawaii
.
Macdonaldite crystallises in the orthorhombic system. Macdonaldite is anisotropic with low relief.
Macdonaldite appears as veins
and fracture coatings in a sanbornite
and quartz
bearing metamorphic rock
. Macdonaldite was first described in 1965 for an occurrence near the Big Creek-Rush Creek area in Fresno County, California
. It has also been reported from Mariposa and Tulare counties in California. It has also been reported from a quarry in San Venanzo
, Umbria
, Italy.
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
silicate mineral with a chemical formula of BaCa4Si16O36(OH)2·10H2O. Macdonaldite was first described in 1965 and named for Gordon Andrew Macdonald (1911-1978) an American volcanologist at the University of Hawaii
University of Hawaii
The University of Hawaii System, formally the University of Hawaii and popularly known as UH, is a public, co-educational college and university system that confers associate, bachelor, master, and doctoral degrees through three university campuses, seven community college campuses, an employment...
.
Macdonaldite crystallises in the orthorhombic system. Macdonaldite is anisotropic with low relief.
Macdonaldite appears as veins
Vein (geology)
In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation...
and fracture coatings in a sanbornite
Sanbornite
Sanbornite is a rare barium phyllosilicate mineral with formula BaSi2O5. Sanbornite is a colorless to white to pale green, platey orthorhombic mineral with Mohs hardness of 5 and a specific gravity of 3.74....
and quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
bearing metamorphic rock
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
. Macdonaldite was first described in 1965 for an occurrence near the Big Creek-Rush Creek area in Fresno County, California
Fresno County, California
Fresno County is a county located in the Central Valley of the U.S. state of California, south of Stockton and north of Bakersfield. As of the 2010 census, it is the tenth most populous county in California with a population of 930,450, and the sixth largest in size with an area of . The county...
. It has also been reported from Mariposa and Tulare counties in California. It has also been reported from a quarry in San Venanzo
San Venanzo
San Venanzo is a comune in the Province of Terni in the Italian region Umbria, located about 30 km southwest of Perugia and about 45 km northwest of Terni...
, Umbria
Umbria
Umbria is a region of modern central Italy. It is one of the smallest Italian regions and the only peninsular region that is landlocked.Its capital is Perugia.Assisi and Norcia are historical towns associated with St. Francis of Assisi, and St...
, Italy.