1. What Is Quartz and What Is It Made Of?
Quartz is said to be the second most common stone in the rocks under the Earth's ground, after feldspar [1]. The material it is made of is "silicon dioxide," which is a simple substance [1]. Despite being so common, this stone is now inside wristwatches and smartphones as a precise component. Why was this common stone trusted with such a special job? The reason lies in a strange property that quartz has.
2. The Piezoelectric Effect the Curie Brothers Discovered in Quartz
In 1880, the French brothers Jacques Curie and Pierre Curie found a strange property in quartz [1]. This property is called the "piezoelectric effect." When force is applied to the crystal, a tiny amount of electricity is born. Conversely, when electricity is applied, the crystal changes shape slightly [1][2]. When electricity is applied to quartz, it vibrates regularly at a fixed speed. By counting this regular vibration, clocks can keep time accurately. However, after this property was discovered, there was still a big wall to cross before it was widely used in electronic devices.
3. Why Natural Quartz Was Not Good Enough for Electronics
Quartz used in electronics needs very high purity and aligned crystal directions. However, natural quartz often has crystals that are not neatly aligned or contains impurities. Therefore, very few natural pieces could be used directly as precise parts. Furthermore, in the first half of the 1900s, places where high-quality natural quartz for electronics could be mined were effectively limited to Brazil. This meant that electronics around the world depended on natural stones dug from one specific country. This could become a big problem.
4. How Synthetic Quartz Took Off After World War II
During World War II, quartz for electronic devices used in radio communication became so important that it was designated as a crucial war material for each country [3]. Researchers in the United States, Germany, and Japan competed to develop methods to create quartz by human power, so they would not have to rely on natural quartz [3]. However, no country won this competition during the war [3]. Actually, the technology to grow synthetic quartz itself existed earlier. In 1845, a German scholar first succeeded in making crystals small enough to be seen with a microscope [1]. From 1898 to 1908, an Italian scholar published a method closer to practical use [4]. But it still took time to make this possible on an industrial scale. After the war ended, Bell Telephone Laboratories in the United States started serious research. They began efforts to grow synthetic quartz in 1946 [1]. In 1950, researchers developed a way to grow quartz using water on a commercial scale. By 1956, this method had reached completion [1]. Thus, the problem that no one solved during the war was finally solved in peacetime.
5. How Synthetic Quartz Is Grown by Hydrothermal Synthesis
The method for making synthetic quartz is called "hydrothermal synthesis." First, high-quality natural quartz is powdered and mixed with a special water solution. It is put into a strong steel container called an "autoclave" [3]. This container is heated from the bottom to about 400 degrees Celsius. The pressure inside is raised to up to about 2,000 times normal air pressure [3]. Then, the quartz powder at the bottom dissolves into the water solution. The solution rises and is carried to the top. At the top of the container, thin plates of quartz called "seed crystals" are placed. The dissolved components slowly pile up on them as crystals [3]. This work takes a long time, about 80 days [3]. The quartz grows slowly at a speed of less than 1 millimeter per day. The grown synthetic quartz crystals are cut into thin plates. They are put into all kinds of electronic devices, like wristwatches, smartphones, and computers. Today, most quartz used as electronic parts is "grown" by human hands using this method [3].
6. Where to Find Synthetic Quartz in Clocks and Smartphones Around You
Inside the clocks and smartphones in your home, there is almost certainly a small quartz crystal grown by hydrothermal synthesis. It is difficult to take them apart, but you can look for the words "Quartz" or "Quartz" on the back of your watch. If you have the chance, try to see natural quartz crystals in a museum or shop that deals with minerals. Imagine that the transparent hexagonal natural crystals and the invisible small crystals working inside your electronics are the same substance called "quartz."