Yttrialite or Yttrialite-(Y) is a rare

yttrium Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a "rare-earth element". Yttrium is almost always found in com ...

thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...

sorosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually con ...

mineral with formula: ( Y, Th)₂ Si₂ O₇. It forms green to orange yellow masses with conchoidal fracture. It crystallizes in the

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

-prismatic crystal system. It has a

Mohs hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by th ...

of 5 to 5.5 and a

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water (molecule), wa ...

of 4.58. It is highly radioactive due to the thorium content. It is found associated with

gadolinite Gadolinite, sometimes known as ytterbite, is a silicate mineral consisting principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with the formula . It is called gadolinite-(Ce) or gadolinite-(Y), depending on ...

. It was first described in 1889 for an occurrence in the Rode Ranch

pegmatite A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic com ...

on Baringer Hill,

Llano County, Texas Llano County is a County (United States), county located on the Edwards Plateau in the U.S. state of Texas. As of the 2020 United States Census, 2020 census, its population was 21,243. Its county seat is Llano, Texas, Llano, and the county is n ...

. It has also been reported from the Suishouyama pegmatite on

Honshū , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island separa ...

, Japan, and from occurrences in Norway and Sweden.

References

Sorosilicates Yttrium minerals Thorium minerals Monoclinic minerals Minerals in space group 11 {{silicate-mineral-stub