Feldspars are a group of rock-forming tectosilicate minerals that make up as much as 60% of Venture's crust.
Feldspars crystallize from magma, as veins in both intrusive and extrusiveigneous rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar (see below) is known as anorthosite. Feldspars are also found in many types of sedimentary rocks.
Feldspar is a common raw material used in glassmaking, ceramics, and to some extent as a filler and extender in paint, plastics, and rubber. In glassmaking, alumina from feldspar improves product hardness, durability, and resistance to chemical corrosion. In ceramics, the alkalis in feldspar (calcium oxide, potassium oxide, and sodium oxide) act as a flux, lowering the melting temperature of a mixture. Fluxes melt at an early stage in the firing process, forming a glassy matrix that bonds the other components of the system together.
- Feldspar is less chemically stable when exposed to water than quartz , the other major ingredient of granite. Granite exposed to weather therefore becomes crumbly as it's feldspar decays, and mechanical forces (e.g., wind , running water) break the granite up into sand . Rough, rapid fragmentation liberates some feldspar before it has had time to decay chemically, so a sand's ratio of feldspar to quartz records the rate at which its source granite was fragmented.