Editing Jasper (section)

==Types==
[[File:Jasper vase WB.71.jpg|thumb|left|Jewel-set vase carved from red-and-yellow jasper. Probable provenance: German, early 17th century, [[Waddesdon Bequest]], [[British Museum]]]]
[[File:Jasper goat basket (Russia, 19 c.).jpg|thumb|Goat-headed basket carved from red jasper. Russian, late 19th century, [[Kremlin Armoury]]]]

Jasper is an [[Opacity (optics)|opaque]] rock of virtually any colour stemming from the mineral content of the original sediments or ash.  Patterns arise during the consolidation process forming flow and depositional patterns in the original silica-rich [[sediment]] or [[volcanic ash]]. [[Hydrothermal circulation]] is generally thought to be required in the formation of jasper.<ref>{{Cite web |title=Jasper |url=https://www.prehistoricoregon.com/learn/what-is-a-mineral/jasper/ |access-date=10 June 2022 |website=Prehistoric Online |language=en-US}}</ref>

Jasper can be modified by the diffusion of minerals along discontinuities providing the appearance of vegetative growth, i.e., [[Dendrite (crystal)|dendritic]]. The original materials are often fractured and/or distorted, after deposition, into diverse patterns, which are later filled in with other colorful minerals. Weathering, with time, will create intensely colored superficial rinds.

The classification and naming of jasper varieties presents a challenge.<ref>{{cite web |title=World of Jaspers |editor=Gamma, Hans |type=main |website=worldofjaspers.com |url=http://www.worldofjaspers.com/index.html}}</ref> Terms attributed to various well-defined materials includes the geographic locality where it is found, sometimes quite restricted such as "Bruneau" (a canyon) and "Lahontan" (a lake), rivers and even individual mountains; many are fanciful, such as "forest fire" or "rainbow", while others are descriptive, such as "autumn" or "porcelain". A few are designated by the place of origin such as a brown Egyptian or red African.

===Banded iron formations ===
Jasper is the main component in the silica-rich parts of [[banded iron formation]]s (BIFs) which indicate low, but present, amounts of dissolved oxygen in the water such as during the [[Great Oxygenation Event|Great Oxidation Event]] or snowball earths.<ref>{{Cite book|title=How to Build a Habitable Planet|last=Broecker|first=W.S.|year=1985}}</ref>  The red bands are microcrystalline red chert, also called jasper.

===Picture jaspers<span class="anchor" id="picture"></span>===
[[File:Jasper earrings.jpg|thumb|Earrings of polished "leopard-spot jasper" (actually a type of spherulitic [[rhyolite]])]]

Picture jaspers exhibit combinations of patterns resulting in what appear to be scenes or images, when seen on a cut section. Such patterns include banding from flow or depositional patterns (from water or wind), as well as dendritic or color variations. Diffusion from a center produces a distinctive [[Orbicular jasper|orbicular]] appearance, i.e., leopard skin jasper or linear banding from a fracture as seen in [[Liesegang rings (geology)|liesegang]] jasper. Healed, fragmented rock produces [[breccia]]ted (broken) jasper.

While these "picture jaspers" can be found all over the world, specific colors or patterns are unique to the geographic region from which they originate. One source of the stone is [[Indonesia]], especially in [[Purbalingga]] district. From the US, [[Oregon]]'s [[Biggs jasper]] and [[Idaho]]'s [[Bruneau jasper]] from the [[Bruneau River]] canyon are particularly fine examples. Other examples can be seen at [[Ynys Llanddwyn]] in [[Wales]].<ref>{{cite web |title=Jasper gemological information |website=gemsociety.org |publisher=International Gem Society (IGS) |url=http://www.gemsociety.org/article/jasper-gem-information/ |access-date=16 January 2015}}</ref> A blue-green jasper occurs in a deposit at Ettutkan Mountain, [[Sibay|Staryi Sibay]], [[Bashkortostan]], Russia. (The town of Sibay, in the far south of the [[Ural Mountains]], near the border with [[Kazakhstan]], is noted for its colossal, open-cast [[copper]] mine.)<ref>{{cite web |title=[green] Jasper from Ettutkanskoe jasper deposit, Ettutkan Mt, Staryi Sibay, Bashkortostan, Russia |website=Mindat.org |url=https://www.mindat.org/locentry-707656.html  |access-date=21 April 2020}}</ref>

===Basanite<span class="anchor" id="basanite"></span> and other types of touchstone===
<blockquote>Basanite is a deep velvety-black variety of amorphous quartz, of a slightly tougher and finer grain than jasper, and less splintery than hornstone. It was the ''Lydian stone'' or ''touchstone'' of the ancients. It is mentioned and its use described in the writings of [[Bacchylides]] about 450&nbsp;BC, and was also described by [[Theophrastus]] in his book ''On Stones'' ([[Ancient Greek]] title: {{math|Περὶ λίθων}}: ''Peri Lithon''), a century later. It is evident that the touchstone that [[Pliny the Elder|Pliny]] had in mind when he wrote about it was merely a dense variety of [[basalt]].<ref>{{cite book |last1=Dake |first1=H.C. |last2=Fleener |first2=Frank L. |last3=Wilson |first3=Ben Hur |year=1938 |title=Quartz Family Minerals: A handbook for the mineral collector |publisher=Whittlesey House (McGraw Hill)}}</ref></blockquote>

Basanite (not to be confused with [[bassanite]]), ''Lydian stone'', and [[radiolarite]] (a.k.a. lydite or flinty slate) are terms used to refer to several types of black, jasper-like rock (also including [[tuff]]s, [[chert]]s and [[siltstone]]s)<ref>{{cite journal |last1=Moore |first1=D.T. |last2=Oddy |first2=W.A. |date=1 January 1985 |title=Touchstones: Some aspects of their nomenclature, petrography and provenance |journal=Journal of Archaeological Science |volume=12 |issue=1 |pages=59–80 |doi=10.1016/0305-4403(85)90015-9 |bibcode=1985JArSc..12...59M }}</ref> which are dense, fine-grained and flinty / cherty in texture and found in a number of localities. The "Lydian Stone" known to the [[Ancient Greeks]] is named for the ancient kingdom of [[Lydia]] in what is now western [[Turkey]]. A similar rock type occurs in [[New England]]. Such rock types have long been used for the making of [[Touchstone (assaying tool)|touchstones]] to test the purity of [[precious metal]] [[alloy]]s, because they are hard enough to scratch such metals, which, if drawn (scraped) across them, show to advantage their metallic [[Streak (mineralogy)|streaks]] of various (diagnostic) colours, against the dark background. There are, confusingly, not one but two rocks called basanite, one being a black form of jasper and the [[Basanite|other]] a black volcanic rock closely akin to basalt. Add to this the fact that many different rock types – having in common the colour black and a fine texture – have, over the ages, been pressed into service as touchstones and it will be seen that there is ample scope for confusion in this [[petrology]]- and [[mineralogy]]-related field of study.<ref>{{cite web |title=Basanite |date=15 October 2012 |website=Mindat.org |url=http://www.mindat.org/min-9173.html |access-date=24 March 2013}}</ref>