Quartz Family

Quartz is a mineral composed of silicon dioxide (SiO2). An abundant mineral, the Quartz family is found commonly all over the world. It develops in various shades, ranging from transparent clarity to opaque, solid colours. It occurs in igneous, metamorphic and clastic rocks (Allaby, 2013), especially in Granite and other felsic formations. It is created through cooling of molten magma, or through precipitation of hot hydrothermal gangue veins. Once crystallised, the Quartz may shift in colour or quality upon further exposure to high temperatures; this is how Amethyst is naturally formed out of clear quartz, and how citrine is naturally formed out of amethyst.

Pebbles of the Quartz Family
(Pebbles of the quartz family, by Cateb Mauro on Flickr.)
Colour range in quartz spans the rainbow. Purple, pink, red, black, brown, earth, green and gold tones encircle a clear quartz pebble.

Quartz has a specific gravity, or density, or 2.65, and a hardness rating on the Mohs scale of 7 (Klein, 1985). Quartz is a trigonal or rhombohedral crystal system; each crystal cell has “six faces, all of which have two pairs of parallel sides” (Allaby, 2013). Vitreous in lustre, it reflects light with a glassy quality (Allaby, 2013). The refractive index of quartz ranges from 1.543–1.553.

Quartz Family showing milky quality
(Quartz can range from total clarity through to a milky quality, to total opacity. By Antranias.)

A testament to its’ hardness on the Mohs scale, the word ‘quartz’ derives from the German word ‘Quarz,’ through the Middle High German, or medieval variant, ‘twarc,’ meaning ‘hard’ or ‘firm.’  

Simply named ‘crystal’ (krystallos / κρύσταλλος) by the Ancient Greeks, the word derives from the Greek word for ice cold, or ‘kryos / κρύος.’ This is due to some philosophers, including the Greek Theophrastus, and the Roman Pliny the Elder, concluding that the mineral in its’ clearest form had to be a form of supercooled, or petrified ice (Tomkieff, 1942).  

Archaeologically, the quartz family was used in prehistoric Ireland alongside flint as a chipped stone attached to tools, used by the living for ‘mundane’ purposes, while also interred in burial mounds and spiritual rituals. Evidence of quartz used in both these methods was found at Lough Gur and the fields of North Mayo (Driscoll & Warren, 2015). Additionally, the ancient site Newgrange, was paved with tiles of quartz lining the exterior of the tomb and “shimmer[s]” in sunlight with an ethereal quality (Driscoll & Warren, 2015).

Further, the Irish Gaelic term for quartz, grianchloch, means ‘sunstone,’ a designation that was supported in the observations of Roman naturalist Pliny the Elder, who observed that quartz could split colours into a light spectrum when held up to sunlight.

Newgrange burial structure lined with quartz tiles
(A landscape of Newgrange, a massive ancient burial structure lined with quartz tiles. By young shanahan on Flickr.)

As early as the 1st Century CE, Pliny the Elder also noted the quartz family as a material used in the manufacture of crystal balls, used in scrying, crystal gazing or fortune telling. Due the clarity of clear quartz, and the colour-refracting nature of the mineral, the crystal was a perfect choice for magical or occult activities due to its seemingly otherworldly behaviour. By the 5th Century, the Catholic Church had outlawed crystal-gazing as a heretical act.

After the reformation of the Church under Henry the VIII, Christendom still held complex feelings towards witchcraft and other magical activities, but entertained research of chemistry, mathematics and astronomy alongside alchemy, divination and astrology.

Vintage Poster of Alexander the Crystal Seer
(A vintage poster of Alexander the Crystal Seer’s stage show, using crystal-gazing. Held by the Library of Congress.)

After the reformation of the Church under Henry the VIII, Christendom still held complex feelings towards witchcraft and other magical activities, but entertained research of chemistry, mathematics and astronomy alongside alchemy, divination and astrology.

Queen Elizabeth I went on to employ Dr. John Dee, a famous polymath, who often used crystal balls in his divination practices (British Museum, 2020). By the Victorian era, crystal gazing had evolved into a far more innocent activity, and was later appropriated by stage magicians and vaudevillian drama as a prop to denote occultism and mysticism, notably by Alexander the Crystal Seer.

Not only has the Quartz family been used extensively for its beauty as a gemstone in jeweling, and being highly suitable for carvings and other aesthetic uses throughout history, it is also heavily utilised as a semiconductor due to its inherent piezoelectricity. This means the crystal develops electric potential when under mechanical stress. Quartz’ piezoelectric nature was discovered by Jacques and Pierre Curie in 1880. Quartz was used for oscillation devices, designed by Bell Labs in 1927, as well as early designs of phonograph pickups, watchmaking and clockwork. 


Quartz Family References

Alexander, C. A. (Claude A. (1910). Alexander, crystal seer sees our life from the cradle to the grave. https://www.loc.gov/pictures/item/2014636876/

Allaby, M. (2020). Quartz. In A Dictionary of Geology and Earth Sciences. Oxford University Press. http://www.oxfordreference.com/view/10.1093/acref/9780198839033.001.0001/acref-9780198839033-e-6907

Antranias. (2014). Krystalkvarts [Photograph, Canon EOS M 35.0mm · ƒ / 5.0 · 1 / 60s · ISO 500]. https://pixabay.com/images/id-238075/

Cateb, M. (2011). Pebbles of the quartz group [Photo]. https://www.flickr.com/photos/mauroescritor/6390595011/

Curie, J., & Curie, P. (1880). Développement par compression de l’électricité polaire dans les cristaux hémièdres à faces inclinées. Bulletin de la Société minéralogique de France, 3(4), 90–93. https://doi.org/10/gg43f2

Darvill, T. (2009). Quartz. In The Concise Oxford Dictionary of Archaeology. Oxford University Press. http://www.oxfordreference.com/view/10.1093/acref/9780199534043.001.0001/acref-9780199534043-e-3408

Dee, J. (n.d.). Crystal ball | British Museum. The British Museum. Retrieved 18 July 2020, from https://www.britishmuseum.org/collection/object/H_SLCups-232

Driscoll, K., & Warren, G. M. (2015). Dealing with the ‘quartz problem’ in Irish lithic research. Lithics – The Journal of the Lithic Studies Society, 0(28), 4. http://journal.lithics.org/index.php/lithics/article/view/402

Driscoll, Killian. (2010). Understanding quartz technology in early prehistoric Ireland. Chapter 3: Quartz lithic technology. [University College Dublin]. https://www.lithicsireland.ie/phd_quartz_lithic_technology_chap_3.html

Klein, C. (1985). Manual of mineralogy. https://archive.org/details/manualofmineralo00klei

Law, J. L., & Rennie, R. R. (2020). Quartz. In J. Law & R. Rennie (Eds.), A Dictionary of Chemistry. Oxford University Press. http://www.oxfordreference.com/view/10.1093/acref/9780198841227.001.0001/acref-9780198841227-e-3468

Pliny the Elder. (n.d.). Natural History, Volume X: Books 36-37 (J. Henderson, Ed.). Retrieved 16 July 2020, from https://www.loebclassics.com/view/LCL419/1962/volume.xml

Sandberg, A. (2008). Quartz [Photo]. https://www.flickr.com/photos/arenamontanus/2756009347/

Tomkeieff, S. I. (1942). On the origin of the name ‘quartz’. Mineralogical Magazine and Journal of the Mineralogical Society, 26(176), 172–178. https://doi.org/10.1180/minmag.1942.026.176.04

Unsplash. (n.d.). Photo by Jen Theodore on Unsplash. Retrieved 18 July 2020, from https://unsplash.com/photos/VPX6eeOI5s4

young shanahan. (2013). Newgrange. [Photo]. https://www.flickr.com/photos/youngshanahan/10645166864/

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