Amethyst is the purple color variety of quartz.
The piezoelectric properties of quartz were discovered in 1880 by Pierre Curie, a French physicist, Nobel Prize, spiritualist, and the pioneer in crystallography, magnetism, piezoelectricity, and radioactivity.
Curie demonstrated that an electric potential was generated when he compressed crystals. Also, when the scientist applied a voltage source to quartz, it began to change shape. This piezoelectric effect produced mechanical vibrations or oscillations of particular frequencies.
Researchers found that the exact frequency at which the crystal oscillates depends on its size, shape, and the temperature does not rely on the energy frequency. This fundamental value is generally called the crystal's "characteristic frequency."
This piezoelectric effect allowed using crystal units for controlling radio frequencies in transmitters and receivers.
At that time, scientists identified the characteristic frequencies of natural quartz species at around 30 kHz. The standard vibration used for quartz clocks and watches was 32768 Hz. The conception of crystal vibrational frequencies came from that time and early studies and applications.
At the beginning of the 20th-century natural quartz was the only material used as a piezoelectric resonator in the crystal oscillators for the first radio, broadcasting stations, sonars during World War I. And during World War II, radio communication became essential for military operations. It caused a spike in crystal bases technologies and manufacturing. Mass production of quartz oscillators became the starting point for all the American electronics industry.
At that time, Brazil was the primary U.S. supplier of crystals necessary to make radiofrequency oscillators. One of the primary quartz from Brazil was the natural Amethyst, so most of the information related to crystal oscillators refers to these purple crystal properties.
Natural quartz and Amethyst became the foundation for further development of communication and electronic devices technologies. Crystals plaid a significant part in the revolutionary change in all our life.
In the new century, synthetic materials replaced natural quartz in the electronics industry developments. However, we still use crystals in our everyday lives, especially for beautification, health, and well-being.