Geological Properties Of Jasper
Geological Properties Of Jasper, Jasper is an opaque form of Chalcedony, which is a microcrystalline variety of the mineral Quartz. It often contains an abundance of impurities, and therefore some regard it as a rock instead of a mineral. Jasper is usually associated with brown, yellow, or reddish colors, but may be used to describe other opaque colors of Chalcedony such as dark or mottled green and orange. Some forms of Jasper are banded, and these banded Jaspers may appear similar to Agate, but unlike Agate they are opaque. When Jasper is dull and lacking interesting colors or patterns, it is not Jasper but rather Chert.
Jasper is an opaque variety of Chalcedony, and is usually associated with brown, yellow, or reddish colours, but may be used to describe other opaque colours of Chalcedony such as dark or mottled green, orange, and black. Jasper is almost always multicoloured, with unique colour patterns and habits.
Jasper, an aggregate of microgranular quartz and/or chalcedony and other mineral phases, is an opaque, impure variety of silica, usually red, yellow, brown or green in colour; and rarely blue. The common red colour is due to iron inclusions. The mineral aggregate 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 snuff boxes. The specific gravity of jasper is typically 2.5 to 2.9. Along with heliotrope (bloodstone), jasper (green with red spots) is one of the traditional birthstones for March. Jaspilite is a banded iron formation rock that often has distinctive bands of jasper.
Geological Properties Of Jasper
History And Introduction:
Jasper is one of the many gemstone varieties of quartz available today. It is an opaque and impure variety of silicon dioxide (SiO2). The name ‘jasper’ is derived from the Greek word for ‘spotted stone’, referring to its typical multicoloured, striped, spotted or flamed appearance. Jasper can form in virtually any colour. Jasper is usually considered a chalcedony, but some scientists classify jasper as a separate type because of its distinctive grainy structure.
Jasper is a dense substance, up to twenty percent of which can be made of foreign materials. Due to these trace impurities, jasper is rarely uniform. In some cases, jasper may even grow together with agate or opal. The patterns of jasper are formed during the process of mineral consolidation, determined by the exact flow and deposition of silica-rich sediments or volcanic ash. Jasper is often modified by other intruding impurities. As original deposits of silica materials naturally form with fissures and cracks after deposition, they are later filled by other minerals, such as iron oxide, manganese dioxide, metal oxide and sometimes organic matter. The final settling of these materials determines the specific appearance of the final substance.
Geological Properties Of Jasper
The most common jasper patterns include interesting marbling and veining, orbital rings, streaks, spots, flaming and banding. Like agate stone, there are numerous trade names and classifications used for jasper today. The names can be very confusing, but fortunately, most are used only by the most avid collectors.
What Do We Do With It:
Jasper has been used as gemstones and other ornamental objects for thousands of years.
In medieval times jasper was said to give the wearer, with God’s help, the power to heal insanity and to heal those possessed by devils. In the fourth century, the wearing of green jasper was said to bring rain and to cure snake bites. Jasper amulets were engraved with passages from the Book of the Dead by the ancient Egyptians to procure safe passage for the deceased in the realm of the dead.
Some of the earliest primitive stone tools (axes) fashioned by man’s ancestors 2.5 million years ago in the Omo valley in Ethiopia, were made of quartz varieties such as jasper or chert. These materials were used because of their hardness and their isotropic brittleness which made it possible to shape the tools with relative ease.
Geological Properties Of Jasper
Jasper is also 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.
Types Of Jasper:
Jasper is an 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. 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 diverse patterns, which are later filled in with other colourful minerals. Weathering, with time, will create intensely coloured superficial rinds.
The classification and naming of jasper varieties 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” or “porcelain”. A few are designated by the place of origin such as a brown Egyptian or red African.
Picture jaspers exhibit combinations of patterns (such as banding from flow or depositional patterns (from water or wind), dendritic or colour variations) resulting in what appear to be scenes or images (on a cut section). Diffusion from a centre 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. While these “picture jasper” can be found all over the world, specific colours or patterns are unique, based upon the geographic region from which they originate. Oregon’s Biggs jasper, and Bruneau jasper from Bruneau Canyon near the Bruneau River in Idaho are known as particularly fine examples. Other examples can be seen at Llanddwyn Island in Wales.
Jasper Crystal Trade Names:
Many stones are given trade names to boost popularity and increase sales. Names often relate to a specific characteristic or the locality where the stone is found.
Dalmatian, leopardskin and zebra jasper exhibit colour or markings similar to the respective animals. Landscape, scenic and picture jasper are all types of mudstone. These varieties usually exhibit markings that resemble a landscape.
Geological Properties Of Jasper
Mookaite from Western Australia is named after Mooka Creek. There are hundreds of different names but many including noreena, polychrome, poppy and imperial offer little or no clue as to the origins or characteristics of the stone.
Countries Of Origin:
Russian Federation; Czechia; Uruguay; United States of America; Madagascar; Portugal; India; Netherlands; Morocco; Unknown; China; Brazil; Mexico; South Africa; Australia; Peru
Identifying Jasper:
Jasper is a variety of quartz with a chemical composition composed primarily of silicon dioxide. Up to 20% percent of fine dense jasper can be composed of foreign materials, typically hematite, pyrolusite, clay or calcite. It has such a distinctly grainy structure compared to other forms of chalcedony that some scientists even put jasper into its own individual group within the quartz family. Jasper has a microcrystalline structure which means its trigonal crystals can only be seen under high magnification. It can be easily distinguished from many other similar materials by its excellent hardness and lack of cleavage.
Popular Varieties:
Biggs
Brecciated
Bumblebee
Florence
Kambaba
Landscape, Picture , Scenic (varieties of mudstone)
Leopardskin
Mookaite (Australian Jasper)
Noreena
Ocean
Orbicular
Owyhee (type of picture jasper)
Polychrome
Snakeskin
Willow Creek
Zebra
Chemical Formula: SiO2
Colour: White, Blue, Red, Green, Yellow, Orange, Brown, Gray, Black, Banded, Multicoloured
Hardness: 6.5 – 7
Crystal System: Hexagonal
Refractive Index: 1.54 – 1.55
SG: 2.63 – 2.65
Transparency: Opaque
Double Refraction: .009
Luster: Vitreous
Streak: White
Cleavage: Indiscernible
Mineral Class: Quartz (Chalcedony)
Crystal Habits: Massive microgranular quartz
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