A gemstone is defined as a natural mineral or organic material that is cut and polished for use in adornment. While countless substances exist, only a small fraction possess the necessary beauty, durability, and availability for widespread use. Rare and highly prized stones often dominate the public imagination, but the most frequently encountered gems in commerce are derived from minerals that are globally abundant. The sheer volume of material required for widespread use necessitates a mineral with a nearly inexhaustible supply.
Identifying the Most Common Gem
The most common mineral used as a gem globally, by a staggering measure of volume, is Quartz. This mineral is a crystalline form of silicon dioxide (SiO2). Since ancient times, varieties of this mineral have served as the principal material for jewelry and carved objects across Europe and Asia. The total volume of Quartz varieties used in adornment far exceeds that of other well-known gem families, such as the Beryl group (Emerald and Aquamarine) or the Corundum group (Ruby and Sapphire). Its ubiquity is a direct result of its massive geological prevalence across all continents.
Geological Abundance and Formation
The commonality of Quartz stems directly from its basic chemical composition: silicon and oxygen, the two most abundant elements in the Earth’s crust. Quartz is second only to the feldspar group in overall crustal abundance, making up approximately 12 percent of the Earth’s lithosphere by mass. Its framework structure consists of silicon-oxygen tetrahedra, creating a stable and chemically resistant mineral.
This stability allows it to form through multiple geological processes. In igneous rocks, Quartz crystallizes from silica-rich magma as it slowly cools, forming a defining constituent of granite and other felsic rocks. It is also prevalent in sedimentary environments, where its resistance to weathering leaves it as the primary mineral in sandstones and residual soils. Furthermore, it forms through precipitation from geothermal fluids, often filling cracks and cavities to create large crystals prized by collectors and cutters.
Common Gemstone Varieties and Usage
Quartz dominates the gem market due to its ability to manifest in a tremendous range of colors and patterns, largely caused by trace impurities or inclusions. Macrocrystalline varieties, where the crystals are visible to the naked eye, include Amethyst, the popular purple gem colored by trace iron and natural irradiation. Citrine, a yellow-to-orange variety, also derives its color from iron impurities, though much commercial material is heat-treated Amethyst.
The microcrystalline and cryptocrystalline varieties are often grouped under the name Chalcedony and are equally widespread in jewelry. These include banded Agate, the opaque red or brown Jasper, and translucent pink Rose Quartz. Quartz registers a 7 on the Mohs scale of hardness, meaning it is resistant to scratching from most common materials and is durable enough for everyday wear. Its durability and low cost make it a favorite for mass-produced jewelry, watch faces, and carved ornamental objects.