feldspar translation in English-French dictionary. en The silica source material may be, for example, feldspars, naturally-occurring zeolites, diatomaceous earths, clinoptilites, mordenites, chabozites, opaline silicas, novaculites, vitreous volcanic rocks (rhyolites, dacites, latites, andesites and their tuffs, and basalts), synthetic glass and high silica rocks (such as quartzite sands ...