Editing Quartz (section)

== Varieties (according to microstructure) ==
Although many of the varietal names historically arose from the color of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Color is a secondary identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties.<ref>{{Cite web|url=https://www.gemselect.com/gem-info/quartz/quartz-info.php|title=Quartz Gemstone and Jewelry Information: Natural Quartz – GemSelect|website=www.gemselect.com|access-date=2017-08-29|archive-url=https://web.archive.org/web/20170829171847/https://www.gemselect.com/gem-info/quartz/quartz-info.php|archive-date=29 August 2017|url-status=live}}</ref>

The most important microstructure difference between types of quartz is that of ''macrocrystalline quartz'' (individual crystals visible to the unaided eye) and the [[microcrystalline]] or [[cryptocrystalline]] varieties ([[Aggregate (geology)|aggregates]] of crystals visible only under high magnification). The cryptocrystalline varieties are either translucent or mostly opaque, while the macrocrystalline varieties tend to be more transparent. [[Chalcedony]] is a cryptocrystalline form of [[silica]] consisting of fine intergrowths of both quartz, and its [[Monoclinic crystal system|monoclinic]] polymorph [[moganite]].<ref name="heany_1994">{{cite journal |last=Heaney |first=Peter J. |year=1994 |title=Structure and Chemistry of the low-pressure silica polymorphs |url=http://rimg.geoscienceworld.org/cgi/content/abstract/29/1/1 |url-status=live |journal=Reviews in Mineralogy and Geochemistry |volume=29 |issue=1 |pages=1–40 |archive-url=https://web.archive.org/web/20110724151910/http://rimg.geoscienceworld.org/cgi/content/abstract/29/1/1 |archive-date=24 July 2011 |access-date=26 October 2009}}</ref> [[Agate]] is a variety of chalcedony that is fibrous and distinctly banded with either concentric or horizontal bands.<ref>{{Cite web |title=Agate |url=https://www.mindat.org/min-51.html |access-date=2025-01-21 |website=www.mindat.org}}</ref> While most agates are translucent, [[onyx]] is a variety of agate that is more opaque, featuring monochromatic bands that are typically black and white.<ref>{{Cite web |title=Onyx |url=https://www.mindat.org/min-2999.html |access-date=2025-01-21 |website=www.mindat.org}}</ref> [[Carnelian]] or sard is a red-orange, translucent variety of chalcedony. [[Jasper]] is an opaque chert or impure chalcedony.<ref>{{Cite web |title=Jasper |url=https://www.mindat.org/min-2082.html |access-date=2025-01-21 |website=www.mindat.org}}</ref>

{| class="wikitable sortable" |
|+ Major varieties of quartz
|-
! Type !! Color and description !! Transparency
!Microstructure 
|-
| [[Herkimer diamond]] || Colorless || Transparent
|Macrocrystalline
|-
| Rock crystal || Colorless || Transparent
|Macrocrystalline
|-
| [[Amethyst]] || Purple to violet colored quartz|| Transparent
|Macrocrystalline
|-
| [[Citrine (quartz)|Citrine]] || Yellow quartz ranging to reddish-orange or brown (Madeira citrine), and occasionally greenish yellow || Transparent
|Macrocrystalline
|-
| [[#Rose quartz|Rose quartz]] || Pink, may display [[Asterism (gemology)|diasterism]] || Transparent
|Macrocrystalline
|-
| [[Chalcedony]] || Fibrous, occurs in many varieties.<br>The term is often used for white, cloudy, or lightly colored material intergrown with [[moganite]]. <br>Otherwise more specific names are used. ||Translucent to opaque
|Cryptocrystalline
|-
| [[Carnelian]] || Reddish orange chalcedony || Translucent
|Cryptocrystalline
|-
| [[Aventurine]] || Quartz with tiny aligned inclusions (usually [[mica]]) that shimmer with [[aventurescence]] || Translucent to opaque
|Macrocrystalline
|-
| [[Agate]] || Multi-colored, concentric or horizontal banded chalcedony || Semi-translucent to translucent
|Cryptocrystalline
|-
| [[Onyx]] || Typically black-and-white-banded or monochromatic agate || Semi-translucent to opaque
|Cryptocrystalline
|-
| [[Jasper]] || Impure chalcedony or chert, typically red to brown but the name is often used for other colors || Opaque
|Cryptocrystalline or Microcrystalline
|-
| [[#Milky quartz|Milky quartz]] || White, may display [[Asterism (gemology)|diasterism]] || Translucent to opaque
|Macrocrystalline
|-
| [[Smoky quartz]] || Light to dark gray, sometimes with a brownish hue || Translucent to opaque
|Macrocrystalline
|-
| [[Tiger's eye]] || Fibrous gold, red-brown or bluish colored chalcedony, exhibiting [[chatoyancy]]. ||Opaque
|Cryptocrystalline
|-
| [[Prasiolite]] || Green || Transparent
|Macrocrystalline
|-
| [[Rutilated quartz]] || Contains [[Acicular (crystal habit)|acicular]] (needle-like) [[Inclusion (mineral)|inclusions]] of [[rutile]] ||Transparent to translucent
|Macrocrystalline
|-
| Dumortierite quartz || Contains large amounts of blue [[dumortierite]] crystals || Translucent
|Macrocrystalline
|}