Garronite-Ca is a fairly rare

silicate mineral 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, the crystalline forms of silica (silicon dio ...

, from the

zeolite Zeolites are a group of several microporous, crystalline aluminosilicate minerals commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ･y where is either a meta ...

, which has been found in a few dozen locations in the world. It was first found in the Glenariff Valley, Garron Plateau,

County Antrim County Antrim (named after the town of Antrim, County Antrim, Antrim, ) is one of the six counties of Northern Ireland, located within the historic Provinces of Ireland, province of Ulster. Adjoined to the north-east shore of Lough Neagh, the c ...

, Northern Ireland, and in some locations in

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

. The name comes from the town of Garron, in Northern Ireland, which is consequently considered its type locality. The name initially used was that of Garronite, without subfixes, but the discovery in 2015 of a garronite with dominant sodium instead of calcium in the position of interchangeable cations made it necessary to use subfixes, remaining as Garronite-Ca, to distinguish it from the new species, Garronite-Na.

Physical and chemical properties

Garronite-Ca is generally found as masses and nodules with a finely fibrous internal structure, white in color, usually showing a concentric growth structure. This causes the nodules to present with a conchoidal fracture. It is very rare as defined crystals. When crystals appear, they usually show the faces corresponding to and .

Localities

Garronite-Ca is formed under

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

conditions at low temperature. It is a rare zeolite, and very rare in the form of defined crystals. As fibrous masses, filling vacuoles in

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

s, it has been found in the county of Antrim, in Northern Ireland (United Kingdom), and in the area of

Fáskrúðsfjörður Fáskrúðsfjörður (; previously named also Búðir ) is a village (''þorp'') in eastern Iceland. It has a population of 735 (as of 2024) and constitutes one of the villages composing the municipality of Fjarðabyggð. Geography Fáskrúðsf ...

(Iceland). It is usually associated with phillipsite, which is located in the outer area of the nodules. As crystals, associated with calcite and analcime, it has been found in San Giorgio di Perlena, Fara Vicentino, Vicenza (Italy) and in Barranc Salat, Calpe, Alicante (Spain).{{Cite journal, last=Calvo, first=Miguel, date=2019, title=Garronite-Ca, analcime, and phillipsite-ca in the Barranc Salat ophite quarry, Calpe, Alicante, Spain, url=https://zenodo.org/record/3633600, journal=Mineral up, volume=5, issue=3, pages=70–71

References

Silicates Silicate minerals Zeolites Calcium minerals