A brief talk on feldspar and its applications
Abstract
The article, authored by Wen Yi of Qing Yuan Boer Fibre Co., Ltd., introduces feldspar — a rock-forming mineral accounting for about 60% of the earth's crust, a mixed crystalline silicate of potassium, sodium, calcium and barium with the general formula M[T4O8]. Industrial feldspar feedstock comes mainly from pegmatites, alkaline rocks and a few acidic dykes related to granite activity; pure feldspar or quartz-feldspar mixtures mostly derive from magmatic differentiation. The feldspar family forms the Or–Ab–An system — potassium feldspar K[AlSi3O8] (pure melting point 1200°C), albite Na[AlSi3O8] (1100°C) and anorthite Ca[AlSi3O8] (1000°C) — and is classified as alkali feldspar, plagioclase and feldspathoids.
On applications: in the glass and ceramics industry feldspar acts as a flux that lowers the firing temperature — in the Al2O3–SiO2 system a liquid phase begins around 985±20°C with feldspar addition, and the more feldspar, the lower the melting temperature. In friction materials, feldspar is used as a friction-increasing filler thanks to its high hardness; the article warns that excessive dosage or overly large grain size can push the friction coefficient up to about 0.6 with loud brake noise. Its conclusion: for friction-industry use, select grain fineness of about 63 μm (250 mesh) or finer.
Key facts
- Occurrence: feldspar is a rock-forming mineral, up to about 60% of the earth's crust
- Chemistry: mixed K/Na/Ca/Ba silicate, general formula M[T4O8]; Or–Ab–An system
- Melting points: pure potassium feldspar 1200°C, albite 1100°C, anorthite 1000°C
- Glass/ceramics: feldspar as a flux — liquid phase begins around 985±20°C in the Al2O3–SiO2 system
- Friction materials: used as a friction-increasing filler for its high hardness
- Warning: too much or too coarse feldspar can push the friction coefficient to about 0.6 with high brake noise
- Recommended fineness: about 63 μm (250 mesh) or finer
- Author: Wen Yi, Qing Yuan Boer Fibre Co., Ltd.
The original article is in Chinese; see the Chinese version for the full text. This page provides the English title, abstract and key facts only — translated and compiled from the original, without full verbatim translation.