Editing Garnet (section)

==Physical properties==
===Properties===
[[File:Garnet.JPG|thumb|left|A sample showing the deep red color garnet can exhibit.]]

Garnet species are found in every colour, with reddish shades most common. Blue garnets are the rarest and were first reported in the 1990s.{{sfn|Klein|Hurlbut|1993|p=600}}<ref>{{cite journal |last1=Galoisy |first1=L. |title=Garnet: From Stone to Star |journal=Elements |date=1 December 2013 |volume=9 |issue=6 |pages=453–456 |doi=10.2113/gselements.9.6.453|bibcode=2013Eleme...9..453G }}</ref><ref name="blue"/><ref>{{cite journal |last1=Baxter |first1=Ethan F. |last2=Caddick |first2=Mark J. |last3=Ague |first3=Jay J. |title=Garnet: Common Mineral, Uncommonly Useful |journal=Elements |date=1 December 2013 |volume=9 |issue=6 |pages=415–419 |doi=10.2113/gselements.9.6.415|bibcode=2013Eleme...9..415B }}</ref>

Garnet species' light transmission properties can range from the gemstone-quality transparent specimens to the opaque varieties used for industrial purposes as abrasives. The mineral's [[lustre (mineralogy)|lustre]] is categorized as [[vitreous lustre|vitreous]] (glass-like) or resinous (amber-like).<ref name="Klein-1993"/>

===Crystal structure===
Garnets are [[Silicate minerals#Nesosilicates or Isosilicates|nesosilicates]] having the general formula ''X''<sub>3</sub>''Y''<sub>2</sub>({{chem|[[silicon|Si]]|[[oxygen|O]]|4}})<sub>3</sub>. The ''X'' site is usually occupied by divalent cations ([[calcium|Ca]], [[magnesium|Mg]], [[iron|Fe]], [[manganese|Mn]])<sup>2+</sup> and the ''Y'' site by trivalent cations ([[aluminium|Al]]<sup>3+</sup>, Fe<sup>3+</sup>, [[chromium|Cr]]<sup>3+</sup>) in an [[octahedron|octahedral]]/[[tetrahedron|tetrahedral]] framework with [SiO<sub>4</sub>]<sup>4−</sup> occupying the tetrahedra.<ref>{{cite web | last = Smyth | first = Joe | title = Mineral Structure Data | work = Garnet | publisher = University of Colorado | url = http://ruby.colorado.edu/~smyth/min/garnet.html | access-date = 2007-01-12 | archive-date = 2007-01-16 | archive-url = https://web.archive.org/web/20070116233247/http://ruby.colorado.edu/~smyth/min/garnet.html | url-status = dead }}</ref>  Garnets are most often found in the [[dodecahedral]] [[crystal habit]], but are also commonly found in the [[trapezohedron]] habit as well as the [[Hexoctahedron|hexoctahedral]] habit.<ref name="Klein-1993" /> They crystallize in the [[Cubic (crystal system)|cubic]] system, having three axes that are all of equal length and perpendicular to one another but are never actually cubic because, despite being isometric, the {100} and {111} families of planes are depleted.<ref name="Klein-1993" /> Garnets do not have any [[Cleavage (crystal)|cleavage]] planes, so, when they fracture under stress, sharp, irregular ([[conchoidal]]) pieces are formed.<ref>{{cite book |last1=Nesse |first1=William D. |title=Introduction to mineralogy |date=2000 |publisher=Oxford University Press |location=New York |isbn=9780195106916 |page=311}}</ref>

<gallery>
File:Pyrope cp.jpg|Crystal structure of pyrope garnet. White spheres are oxygen; black, silicon; blue, aluminium; and red, magnesium.
File:Pyrope crystal structure.jpg|Same view, with ion sizes reduced to better show all ions
File:Pyrope si.jpg|Silicon ion size exaggerated to emphasize silica tetrahedra
</gallery>

===Hardness===
Because the chemical composition of garnet varies, the atomic bonds in some species are stronger than in others. As a result, this mineral group shows a range of hardness on the [[Mohs scale of mineral hardness|Mohs scale]] of about 6.0 to 7.5.<ref>{{Cite book|last1=Deer|first1=W. A.|url=https://pubs.geoscienceworld.org/books/book/952/An-Introduction-to-the-Rock-Forming-Minerals|title=An Introduction to the Rock-Forming Minerals|last2=Howie|first2=R. A.|last3=Zussman|first3=J.|publisher=Mineralogical Society of Great Britain and Ireland|year=2013|isbn=9780903056434|chapter=Garnet Group}}</ref> The harder species like [[almandine]] are often used for abrasive purposes.<ref>{{cite journal |last1=Perec |first1=Andrzej |title=Disintegration and recycling possibility of selected abrasives for water jet cutting |journal=DYNA |date=1 October 2017 |volume=84 |issue=203 |pages=249–256 |doi=10.15446/dyna.v84n203.62592|doi-access=free }}</ref>

===Magnetics used in garnet series identification===
For gem identification purposes, a pick-up response to a strong [[neodymium magnet]] separates garnet from all other natural transparent gemstones commonly used in the jewelry trade. [[Magnetic susceptibility]] measurements in conjunction with refractive index can be used to distinguish garnet species and varieties, and determine the composition of garnets in terms of percentages of end-member species within an individual gem.<ref>D. B. Hoover, B. Williams, C. Williams and C. Mitchell, [http://www.stonegrouplabs.com/magnetics_garnetchemistry.pdf Magnetic susceptibility, a better approach to defining garnets] {{Webarchive|url=https://web.archive.org/web/20111005095124/http://www.stonegrouplabs.com/magnetics_garnetchemistry.pdf |date=2011-10-05 }}, The Journal of Gemmology, 2008, Volume 31, No. 3/4 pp. 91–103</ref>