Rock Crystal (Clear Quartz)
SiO₂
Quick Facts
About Rock Crystal (Clear Quartz)
Rock Crystal is the purest form of quartz—a gemstone that is completely colorless and transparent. For centuries, it was believed to be 'eternal ice' frozen so hard it would never melt. It is the defining mineral for a hardness of 7 on the Mohs scale and is the most common mineral found on the Earth's continental crust. Its name comes from the Greek 'krystallos', meaning ice.
Formation & Geology
Quartz forms in almost all geological environments: igneous, metamorphic, and sedimentary. Rock crystal specifically grows from silica-rich hydrothermal solutions in veins and geodes. It often forms beautiful, six-sided prisms ending in a pyramid shape. Because it is so stable and resistant to weathering, it is the primary component of most sand beaches.
Physical Characteristics
Quartz has a hardness of 7 and no cleavage, meaning it breaks with a conchoidal (shell-like) fracture. It is piezoelectric, which means it generates an electric charge when mechanical pressure is applied. This unique property makes rock crystal essential in modern electronics. It is transparent and has a vitreous luster. If perfectly pure, it is completely clear; any color indicates the presence of trace elements or radiation damage.
Historical & Modern Significance
In ancient Japan, rock crystal was considered the 'perfect jewel'—a symbol of purity and infinite space. In medieval Europe, it was carved into 'crystal balls' for scrying and divination. Today, while still a popular gemstone and ornamental material, its most critical use is in technology. Synthetic quartz is used in billions of watches, computers, and cell phones due to its precise vibration frequency (piezoelectricity).
Colors & Varieties
Colorless, transparent
Key Properties
- Completely transparent quartz
- Defining mineral for Hardness 7
- Strongly piezoelectric
- Hexagonal prism habit
- No cleavage
- Highly stable and durable
Uses & Applications
- Jewelry and ornaments
- Crystal balls and carvings
- Electronics (oscillators)
- Optical lenses and prisms
- Glass manufacturing (industrial)
Where to Find
- Brazil - world's largest producer
- United States (Arkansas)
- Madagascar
- Alps (Europe)
- Namibia
- Russia