Quartz vs Feldspar
Quartz and Feldspar are minerals that are found prominently in the earth’s crust. In fact, more than 60% of the earth’s crust is made up of Feldspars. Feldspars are formed when magma solidifies into igneous rocks. However, it is also found in many metamorphic and sedimentary rocks. On the other hand, quartz is an oxide of silica that is abundantly found in the earth’s crust. Some of varieties of quartz are considered semiprecious gemstones. Because of their structural similarities, many people remain confused between quartz and feldspar. This article attempts to highlight the differences between these two most important rock forming minerals.
If one tries to look at important elements that make up the earth’s crust, it becomes clear that 99% of the crust is made up of 8 elements namely oxygen, aluminum, silicon, magnesium, iron, calcium, potassium and sodium. The composition of rocks is mostly in the form of oxides because of oxygen being dominant anion. Thus, most minerals are found and reported in the form of their oxides and combinations of oxides. The most abundant oxide in the earth’s crust is SiO2, also called quartz. Next most abundant are oxides of aluminum, that form a bulk of feldspars. Feldspars contain not just aluminum oxide but oxides of calcium, sodium, and potassium also.
In general, igneous rocks are classified on the basis of their silica and aluminum contents. Rocks with high silica content are those that are quartz, while rocks with excess aluminum content are called feldspars.
Nearly 20 MT of feldspar was produced in the world last year, mostly by Italy, Turkey, and China. Feldspar is mostly used in glass and ceramics industry, and as a filler in paints, rubber, and plastics industries. In glasses, feldspar increases hardness and durability, while also helping in prevention of chemical corrosion. Feldspar is widely used in making kitchenware.
On the other hand, quartz is mainly used in gemstone industry, as well as, a piezoelectric material in electronic industry. Chief quartz producing countries of the world are Brazil, India, Germany, US, and France. Quartz is harder than feldspar. If compared on Mhos scale, feldspar scores 6 while quartz scores 7. If we compare colors, we find that feldspars are mostly light colored, whereas quartz are found in all sorts of colors depending upon impurities present. Thus, we have dark brown, as well as, dark purple colored quartz, whereas feldspars are limited to pink, light gray and green only.
What is the difference between Quartz and Feldspar?
• Both feldspar as well as quartz are rock forming minerals.
• While quartz is oxide of silica, aluminum is the main element whose oxide is referred to as feldspar.
• Quartz is harder, at 7 on Mhos scale, than feldspar ( 6 on Mhos scale).
• Feldspar is mostly light colored, whereas quartz is found in a variety of colors, even dark colored like brown and purple because of presence of impurities.
• Quartz is used in gemstone industry and in electronics because of its piezoelectric property
• Feldspar is used in glass and ceramic industry. It is also use as filler in paint, plastic and rubber industry. Dinnerware and tiles are also made using feldspar.