Editing Crystal (section)

{{Short description|Solid material with highly ordered microscopic structure}}
{{redirect|Crystalline|the Björk song|Crystalline (song)}}
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{{about|crystalline solids|other uses|Crystal (disambiguation)}}
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[[File:Quartz 28.jpg|thumb|upright=1.25|Crystals of [[amethyst]] [[quartz]]]]
[[File:Crystalline polycrystalline amorphous2.svg|thumb|upright=1.25|Microscopically, a [[single crystal]] has atoms in a near-perfect [[Periodic function|periodic]] arrangement; a polycrystal is composed of many microscopic crystals (called "[[crystallite]]s" or "grains"); and an [[amorphous]] solid (such as [[glass]]) has no periodic arrangement even microscopically.]]

A '''crystal''' or '''crystalline solid''' is a [[solid]] material whose constituents (such as [[atom]]s, [[molecule]]s, or [[ion]]s) are arranged in a highly ordered microscopic structure, forming a [[crystal lattice]] that extends in all directions.<ref>{{cite web |title=Chem1 online textbook—States of matter |url=http://www.chem1.com/acad/webtext/states/states.html#SEC4 |author=Stephen Lower |access-date=2016-09-19}}</ref><ref>{{cite book |last1=Ashcroft |last2=Mermin |name-list-style=and |title=[[Ashcroft and Mermin|Solid State Physics]] |year=1976}}</ref> In addition, macroscopic [[single crystal]]s are usually identifiable by their [[Geometry|geometrical shape]], consisting of flat [[face (geometry)|faces]] with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as [[crystallography]]. The process of crystal formation via mechanisms of [[crystal growth]] is called [[crystallization]] or [[solidification]].

The word ''crystal'' derives from the [[Ancient Greek]] word {{lang|grc|κρύσταλλος}} ({{transliteration|grc|''krustallos''}}), meaning both "[[ice]]" and "[[Quartz#Varieties (according to color)|rock crystal]]",<ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dkru%2Fstallos κρύσταλλος], [[Henry George Liddell]], [[Robert Scott (philologist)|Robert Scott]], ''A Greek-English Lexicon'', on Perseus Digital Library</ref> from {{lang|grc|κρύος}} ({{transliteration|grc|''kruos''}}), "icy cold, frost".<ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dkru%2Fos κρύος], Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus Digital Library</ref><ref>{{cite web |title=crys·tal |work=The American Heritage Dictionary of the English Language |url=https://www.ahdictionary.com/word/search.html?q=crystal&submit.x=0&submit.y=0 |access-date=2023-06-17}}</ref>

Examples of large crystals include [[snowflake]]s, [[diamond]]s, and [[table salt]]. Most inorganic solids are not crystals but [[polycrystal]]s, i.e. many microscopic crystals fused together into a single solid. Polycrystals include most [[metals]], rocks, [[ceramics]], and [[ice]]. A third category of solids is [[amorphous solid]]s, where the atoms have no periodic structure whatsoever. Examples of amorphous solids include [[glass]], [[wax]], and many [[plastic]]s.

Despite the name, [[lead glass|lead crystal, crystal glass]], and related products are ''not'' crystals, but rather types of glass, i.e. amorphous solids.

Crystals, or crystalline solids, are often used in [[pseudoscientific]] practices such as [[crystal therapy]], and, along with [[gemstone]]s, are sometimes associated with [[Spell (paranormal)|spellwork]] in [[Wicca]]n beliefs and related religious movements.<ref>Regal, Brian. (2009). ''Pseudoscience: A Critical Encyclopedia''. Greenwood. p. 51. {{ISBN|978-0-313-35507-3}}</ref><ref>{{cite web |url=http://paganwiccan.about.com/od/spellworkfolkmagic/ss/Magical-Crystals-And-Gemstones.htm#showall |title=Using Crystals and Gemstones in Magic |date=31 August 2016 |author=Patti Wigington |website=[[About.com]] |access-date=14 November 2016 |archive-date=15 November 2016 |archive-url=https://web.archive.org/web/20161115193403/http://paganwiccan.about.com/od/spellworkfolkmagic/ss/Magical-Crystals-And-Gemstones.htm#showall |url-status=dead }}</ref><ref>{{cite web |url=http://witcheslore.com/bookofshadows/healing/the-magic-of-crystals-and-gemstones/4765/ |title=The Magic of Crystals and Gemstones |date=14 December 2011 |website=WitchesLore |access-date=14 November 2016}}</ref>