Feldspar
A variety of Minerals
What is Feldspar?
Feldspars (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar is known as anorthosite. Feldspars are also found in many types of sedimentary rocks.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Feldspar before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Feldspar Localities Map
See where Feldspar is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Key Characteristics
Composition of Feldspar
The structure of a feldspar crystal is based on aluminosilicate tetrahedra. Each tetrahedron consists of an aluminium or silicon ion surrounded by four oxygen ions. Each oxygen ion, in turn, is shared by a neighbouring tetrahedron to form a three-dimensional network. The structure can be visualized as long chains of aluminosilicate tetrahedra, sometimes described as crankshaft chains because their shape is kinked. Each crankshaft chain links to neighbouring crankshaft chains to form a three-dimensional network of fused four-member rings. The structure is open enough for cations (typically sodium, potassium, or calcium) to fit into the structure and provide charge balance.
Quick Facts
Physical Properties
- Color
- Colourless, yellow, green, blue-green, orange, red-brown, dark gray, gray-black
- Density
- 2.56 g/cm³
- Streak
- White
Chemical Properties
- Chemical Formula
- KAlSi3O8–NaAlSi3O8–CaAl2Si2O8
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Feldspar FAQs
How do I identify Feldspar?
Feldspar can be identified by its Colourless color. Look for these key characteristics when examining specimens.
What color is Feldspar?
Feldspar typically appears in Colourless, yellow, green, blue-green, orange, red-brown, dark gray, gray-black. Color can vary depending on impurities and formation conditions.
What is the composition of feldspar of Feldspar?
The structure of a feldspar crystal is based on aluminosilicate tetrahedra. Each tetrahedron consists of an aluminium or silicon ion surrounded by four oxygen ions. Each oxygen ion, in turn, is shared by a neighbouring tetrahedron to form a three-dimensional network. The structure can be visualized as long chains of aluminosilicate tetrahedra, sometimes described as crankshaft chains because their shape is kinked. Each crankshaft chain links to neighbouring crankshaft chains to form a three-dimensional network of fused four-member rings. The structure is open enough for cations (typically sodium, potassium, or calcium) to fit into the structure and provide charge balance.
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