kvartsandelen

Kvartsandelen refers to the proportion of quartz present in a rock, sediment, or material, usually expressed as a percentage by volume or by mass. It is a fundamental descriptor of mineral composition in geology and related fields and influences several physical and chemical properties of the material.

In geology, kvartsandelen is used in both classification and interpretation. In igneous petrology, quartz content is a key component in the QAPF classification diagram, helping distinguish felsic rocks from intermediate and mafic ones. In sedimentology and soil science, the quartz fraction affects density, porosity, weathering resistance, and durability of the material. In industrial contexts, higher quartz content often correlates with greater chemical inertness and hardness, making quartz-rich materials desirable for glassmaking, ceramics, and abrasive applications.

Measurement and estimation methods include thin-section petrography with point counting to determine quartz modal abundance, X-ray diffraction and Rietveld refinement for bulk quartz fraction, and automated image analysis for grain-scale quantification. In sands, kvartsandelen is commonly determined by similar mineralogical analyses, sometimes complemented by physical separation techniques to isolate quartz.

Formation and variation: quartz is chemically stable under surface conditions, so mature sediments and continental crust tend to have higher kvartsandelen. The quartz content reflects provenance, transport distance, diagenesis, and metamorphic history. Weathering of feldspathic rocks preferentially removes feldspar, often increasing the relative quartz content over time.

Typical ranges: in sands, quartz content commonly ranges from around 50% to well over 90%. High-purity quartz sands used in glass manufacturing often exceed 95% quartz. Quartzite and many granitic rocks exhibit very high quartz fractions, while lithic and feldspathic rocks show lower values.