Chemistry:Feldspathoid
The feldspathoids are a group of tectosilicate minerals which resemble feldspars but have a different structure and much lower silica content. They occur in rare and unusual types of igneous rocks, and are usually not found in rocks containing primary quartz. A notable exception where feldspathoids and quartz-bearing rocks are found together is the Red Hill Syenite.[1]
Foid, a contraction of the term feldspathoid, is applied to any igneous rock containing up to 60% modal feldspathoid minerals. For example, a syenite with significant nepheline present can be termed a nepheline-bearing syenite or nepheline syenite, with the term nepheline replaceable by any foid mineral. Such terminology is used in the Streckeisen (QAPF) classification of igneous rocks.[2]
Feldspathoid minerals
- Chemistry:Afghanite – Tectosilicate mineral
- Chemistry:Analcime – Tectosilicate mineral
- Chemistry:Cancrinite – Feldspathoid mineral
- Chemistry:Kalsilite – Vitreous white to grey feldspathoidal mineral
- Chemistry:Leucite – Potassium and aluminium tectosilicate mineral
- Chemistry:Nepheline – Silica-undersaturated aluminosilicate mineral
- Chemistry:Petalite – Silicate mineral, used in ceramic glazing
- Sodalite Group
- Chemistry:Hauyne – Silicate mineral
- Chemistry:Lazurite – Alumino-silicate mineral whose blue colour is due to a sulfide species and not copper
- Chemistry:Nosean
- Chemistry:Sodalite – Blue tectosilicate mineral
- Chemistry:Tugtupite
References
- ↑ "The Feldspathoid Group of Minerals". Amethyst Galleries, Inc.. http://www.galleries.com/minerals/silicate/feldspat.htm.
- ↑ Allaby, Ailsa; Allaby, Michael (1999). A Dictionary of Earth Sciences. Oxford University Press.
 |  |
