Quartz is an inorganic form of silica with hardness and no cleavage, making it highly valued as a semi-precious stone for carving and cameo work in ancient times.

Crystalline quartz is now used in watches, clocks, radios and cell phones as oscillators components, in addition to being integrated into numerous other devices like electronic meters.

Translucent

Quartz, the second most abundant mineral on Earth, occurs at all temperatures and can be found in all kinds of rocks including igneous, metamorphic and sedimentary formations. Quartz typically displays transparent to translucent properties; minor impurities create various colors. Quartz may either have macrocrystalline or cryptocrystalline crystal structures with cryptocrystalline varieties exhibiting vitreous (glass-like) surfaces that often line open voids while macrocrystalline varieties show hexagonal prisms or pyramid-like ends that display translucent white, yellow, green or gray tones instead. Quartz does not display cleavage; fractures typically involve conchoidal surfaces rather than flat surfaces (cleavage).

Ancient Greeks called quartz “krystallos,” meaning ice, due to its transparency. Quartz allows light to pass easily through it while slight chemical impurities create different color varieties such as amethyst and rose quartz; other variations may include cloudy white crystals known as “smoky or milky quartz.”

Hard

Hardness of minerals is determined by their microstructure at an atomic level and depends on the strength of bonds between atoms. Frederich Mohs developed his famous Mohs scale of mineral hardness in 1822; this scale ranks minerals according to their ability to scratch other known specimens, with diamond being considered the hardest mineral specimen on this list.

Mohs Scale of Hardness Levels. Although non-linear in their difference, using Mohs to identify mineral is relatively straightforward: place any unidentified mineral against an external reference material like fingernail (2.5), penny (1.00), quartz crystal (7) or steel file 6.5-7.5 in hardness levels before testing with Mohs scale (9).

Quartz crystal has an extremely high Mohs rating of 10, making it difficult to scratch. By conducting the fingernail test, it should be possible to distinguish it from soft calcite which only has a rating of 3. If your mineral has the ability to scratch glass though, such as Gilalite which only scores 4, then chances are good you have found a Quartz crystal!

Piezoelectric

Quartz crystals possess the unique property of being able to generate electric charges through mechanical stress. This phenomenon, known as piezoelectricity, makes this material highly sought-after.

When crystals are squeezed or expanded, they create an imbalanced net positive charge on one face and negative charge on another. Once wired up, positively charged faces attract electrons while negatively charged faces repel them – producing voltage and thus the piezoelectric effect is complete.

Quartz crystal’s piezoelectric properties allow it to be utilized in an array of devices. For instance, clockmakers use quartz crystal to vibrate at a precise rate and generate pulses of electricity that keep track of seconds, minutes and hours. Ultrasound equipment including scanners, microphones and acoustic transducers also utilize quartz crystal as do specialized lenses and windows used in lasers, microscopes and telescopes.

Non-cleavage

Cleavage can be used to identify minerals. Cleavage refers to the tendency of crystalline materials to crack along distinct planes of weakness in their crystal structure and breaks along specific planes where bonding between atoms is weaker; it shows which direction bonding is less secure between atoms than elsewhere in its crystal structure.

Cleavage can be an invaluable way to gain insights into a mineral’s inner structure, but not all minerals show signs of it. Quartz, for instance, does not exhibit any cleavage and fractures irregularly instead. When this occurs it is termed non-cleavaged fractured mineral or conchoidal hackly to describe this feature.

Some minerals exhibit cleavage angles parallel to potential crystal faces, while others exhibit acute or obtuse angles over short surfaces, and still others possess nearly rectangular or squared edges on long surfaces. Quartz shows diagonal cleavage lines as seen in this sample’s PP view – it also contains needles of sillimanite as well as fragments of biotite and magnetite in its composition.