Jasper
 
Jasper is an ornamental rock composed mostly of chalcedony, microcrystalline Quartz, in association with other minerals, which give it colorful bands and patterns.    Jasper was a favorite gem in history; its name can be traced back in Hebrew, Assyrian, Persian, Greek and Latin.
 
Jasper is often named according to its pattern: landscape Jasper, the most popular, offers a small panorama in stone.   Ribbon Jasper, Picture Jasper, and Orbicular Jasper are the names of other varieties.  Jasper is found in many countries.  It is sometimes used to create bowls and other objects and to adorn buildings, such as the Saint Wenceslas Chapel in Prague.
 
Jasper is a form of chalcedony which is  an opaque, impure variety of silica.   It is usually red, yellow, brown or green, and rarely blue.   This mineral breaks with a smooth surface and is used for ornamentation or as a gemstone.   It can be highly polished and is used for vases, seals and, at one time, for snuff boxes.   When the colors are in stripes or bands, it is called striped or banded Jasper.   Jaspilite is a banded iron formation rock that often has distinctive bands of Jasper.   Jasper is an opaque, fine-grained, compact variety of cryptocrystallilne Quartz - long used for making arrowheads, spearheads, knives and other useful objects called chert.  Jasper owes its red color to iron III inclusions.   The specific gravity of Jasper typically runs 2.5 to 2.9.
 
The name means spotted or speckled stone and is derived via Old French jaspre (variant of Anglo-Norman jaspe) and Latin iaspidem (nom. iaspis) from Greek ἴασπις iaspis, (feminine noun) from a Semitic language(cf. Hebrew יושפה yushphah, Akkadian yashupu), ultimately from Persian یشپ yašp.  Green jasper was used to make bow drills in Mehrgarh between 4th-5th millennium BC.  Jasper is known to have been a favorite gem in the ancient world; its name can be traced back in Arabic, Persian, Hebrew, Assyrian, Greek and Latin.  On Minoan Crete within present day Greece, Jasper was carved to produce seals circa 1800 BC, as evidenced by archaeological recoveries at the palace of Knossos.
 
Jasper is an opaque rock of virtually any color 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.
 
Jasper can be modified by the diffusion of minerals along discontinuities providing the appearance of vegetative growth, i.e., dendritic.  The original materials are often fractured and/or distorted, after deposition, into myriad beautiful patterns which are to be later filled with other colorful minerals.  Weathering, with time, will create intensely colored superficial rinds.
 
The classification and naming of Jasper presents a challenge.  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", "Porcelain" or "Dalmatian".  A few are designated by the country of origin, such as a Brown Egyptian or Red African leaving tremendous latitude in the naming of Jasper material.
 
Picture Jaspers exhibit combinations of patterns (such as banding from flow or depositional patterns, from water or wind, dendritic or color variations) resulting in what appear to be scenes or images, on a cut section.  Diffusion from a center produces a distinctive orbicular appearance, i.e., Leopard Skin Jasper, or linear banding from a fracture as seen in Leisegang Jasper.  Healed, fragmented rock produces brecciated (broken) Jasper.  Examples of this can be seen at Llanddwyn Island in Wales.
 
The term basanite has occasionally been used to refer to a variety of Jasper, for example a black flinty or cherty Jasper found in several New England states of the USA.  Such varieties of Jasper are also informally known as Lydian stone or lydite and have been used as touchstones in testing the purity of precious metal alloys.
 
 
 
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