Jasper

Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron(III) inclusions. Jasper breaks with a smooth surface and is used for ornamentation or as a gemstone. It can be highly polished and is used for items such as vases, seals, and snuff boxes. The density of jasper is typically 2.5 to 2.9 g/cm3. Jaspillite is a banded-iron-formation rock that often has distinctive bands of jasper.

Jasper

General

Category Aggregate rock (impure chalcedony variety)

Formula SiO2 (with varying impurities)

Crystal system Hexagonal

Identification

Colour Most commonly red, but may be yellow, brown, green or (rarely) blue

Cleavage Indiscernible

Mohs scale hardness 6.5–7

Luster Vitreous

Diaphaneity Opaque

Specific gravity 2.5–2.9

Refractive index 1.54–2.65

Birefringence 0.009

Etymology and history

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 an Afroasiatic language (cf. Hebrew ישפה yashpeh, Akkadian yashupu). This Semitic etymology is believed to be unrelated to that of the English given name Jasper, which is of Persian origin, though the Persian word for the mineral jasper is also yashum (یَشم).

Green jasper was used to make bow drills in Mehrgarh between 4th and 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, jasper was carved to produce seals circa 1800 BC, as evidenced by archaeological recoveries at the palace of Knossos.

Although the term jasper is now restricted to opaque quartz, the ancient iaspis was a stone of considerable translucency including nephrite. The jasper of antiquity was in many cases distinctly green, for it is often compared to emerald and other green objects. Jasper is referred to in the Nibelungenlied as being clear and green. The jasper of the ancients probably included stones which would now be classed as chalcedony, and the emerald-like jasper may have been akin to the modern chrysoprase. The Hebrew word may have designated a green jasper. Flinders Petrie suggested that the odem – the first stone on the High Priest's breastplate – was a red jasper, whilst tarshish, the tenth stone, may have been a yellow jasper.

Characteristics

Jasper is very rarely found in its pure form. Its chemical and physical properties vary considerably due to intergrowths with agate and opal, as well as impurities of up to 20%, such as aluminum oxide, iron oxide, iron hydroxide, and manganese hydroxide. Since the quantity and distribution of these impurities determine its appearance, jasper's color and variety are extraordinarily broad. Furthermore, the streak color also changes depending on the impurities and is difficult to use for authenticity testing.

As a result, many similarly shaped and grained minerals or varieties and even rocks whose color and pattern are similar to those of jasper are sold under this name.

Types

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 colorful minerals. Weathering, with time, will create intensely colored 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.

Banded iron formations

Jasper is the main component in the silica-rich parts of banded iron formations (BIFs) which indicate low, but present, amounts of dissolved oxygen in the water such as during the Great Oxidation Event or snowball earths. The red bands are microcrystalline red chert, also called jasper.

Picture jaspers

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 appearance, i.e., leopard skin jasper or linear banding from a fracture as seen in liesegang jasper. Healed, fragmented rock produces brecciated (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. A blue-green jasper occurs in a deposit at Ettutkan Mountain, 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.)

Basanite and other types of touchstone

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 BC, and was also described by Theophrastus in his book On Stones (Ancient Greek title: Περὶ λίθων: Peri Lithon), a century later. It is evident that the touchstone that Pliny had in mind when he wrote about it was merely a dense variety of basalt.

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 tuffs, cherts and siltstones) 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 touchstones to test the purity of precious metal alloys, because they are hard enough to scratch such metals, which, if drawn (scraped) across them, show to advantage their metallic 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 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.

Varieties

The names or trade names of the many varieties often reflect their place of origin, but also their color and pattern.

Agate jasper (also jaspagate) is a yellow, brown and green striped intergrowth of jasper and agate, strictly speaking a rock.

Egyptian jasper, also known as spherical jasper, Nile pebble, or jasper nodule, is ochre-yellow to brown and brick-red, often striped and flamed, and is found in large quantities as gravel in the Nile and the desert. Near Cairo, it forms a conglomerate that probably belongs to the Cretaceous formation.

Due to its grey, green, yellow, red and brown coloured, parallel striped or banded structure, the banded jasper is predestined for processing into gems.

The fine-grained, black basanite is particularly well known to jewelers and goldsmiths, as they use it as a sample.

Due to its multifaceted nature, picture jasper, with its brown and black veining, is often confused with mookaite, epidote, pietersite, stromatolite, and tiger iron. Picture jasper is mined primarily in South Africa, Oregon, and Australia.

Dalmatian jasper is a variety with a grey to beige body and black speckles, which owes its name to the dog breed of the same name.

Hornstone, which is often used as a synonym for jasper, is also fine-grained, but has a grey to brown-red, and rarely green to black colour.

The Kellerwald agate (found in Kellerwald / Northern Hesse) is a white-veined red jasper.

Often imitated by similar-looking rocks, landscape jasper (also called Kalahari jasper) displays vivid patterns on its surface that, with little imagination, can be interpreted as stylized landscapes or plants. The brown color, caused by iron admixtures, further reinforces this impression.

Mookaite is a pink to light red variety with a cloud-like banded structure that is mainly mined in Australia.

A white-grey or yellowish-to-brownish-red variety named after its location in Nunkirchen is known as Nunkirchen Jasper. It is often dyed with Prussian Blue and sold as an imitation lapis lazuli under the trade names German Lapis, Swiss Lapis, or Nunkirchen Lapis Lazuli.

Ocean Jasper comes from the Marovato Mine in Madagascar, which has been known since 2001. In esoteric circles, it is also known as eye jasper or agate, as well as spherical rhyolite or chalcedony.

Porcelain jasper (also porcelanite) is the no longer used name for various rocks that formed from clay or sandstone under high temperatures and low pressures. They are often found as contact metamorphoses in basalt chimneys or coal seams, where they were formed during coal seam fires. Localities include Epterode near Großalmerode in Hesse (Bühlchen Jasper), or Planitz near Zwickau. Although there is sometimes an external similarity to jasper (bright colors and sometimes – with a high glass content – conchoidal fracture), these rocks have nothing to do with jasper in the mineralogical sense. The correct term is fritted rock or buchite. 

The misleading, but still used, term Prasem refers on the one hand to a fine-grained, washed-out green jasper variety, but on the other hand also to a leek-green quartz aggregate.

Plasma is quite similar to praseme, but has a rather coarse-grained structure, so its green color appears dirty.

Silex is the name given to the yellow and reddish-brown spotted or concentrically striped variety, mostly red and brown, also yellowish and black, found especially on ironstone veins in many places.

Indian zebra jasper is dark brown with light brown streaks and often contains fossilized shells and snails.

Although heliotrope is often mistakenly referred to as blood jasper, it is actually a distinct quartz variety with a leek-green color and pink to red flecks. Unlike granular jasper, however, heliotrope has a radial structure, but can resemble jasper by forming spherical aggregates.

Use as tools

Jasper was used to make bow drills, to light fires, in Mehrgarh, between the 4th and 5th millennium BC. Phthanite was used to make prehistoric tools in Brittany. Jasper was also used to cut tools: this is the case of Fontmaure jasper, for example, but also, very locally, of Brittany jasper.

Use as a gemstone

Jasper is known to have been the preferred jewel in the ancient world, its name can be traced in Arabic, Persian, Hebrew, Assyrian, Greek and Latin. On the Minoan island of Crete, jasper was carved to produce seals around 1800 BC, as evidenced by archaeological finds in the Palace of Knossos. Jasper was a highly valued gemstone among the ancient Greeks and Romans.

The Bible says about the Heavenly Jerusalem revealed to the Apostle John:

“The foundation stones of the city wall are adorned with all kinds of precious stones; the first foundation stone is a jasper, the second a sapphire, the third a chalcedony, the fourth an emerald, the fifth a sardonyx, the sixth a carnelian, the seventh a chrysolite, the eighth a beryl, the ninth a topaz, the tenth a chrysoprase, the eleventh a jaacinth and the twelfth an amethyst.”

– (Rev 21:19)

Over the centuries, jasper has lost importance and value and is currently used for seal stones, boxes, vases, table tops, jugs, mosaics, architectural works, etc.

The largest polished green jasper is a profiled bowl in the Hermitage Museum in Saint Petersburg, measuring 5.04 × 3.22 meters. The bowl, also known as the Kolyvan Vase, made of Revnev jasper from the Altai region weighs approximately 19 tons, has a circumference of about 12.7 meters, and a height of about 2.57 meters. 

Another polished red jasper was made from a 2850 kg blank into a sphere weighing about one ton and 87.5 cm in diameter. It is located in Sankt Augustin - Hangelar. 

Another large jasper sphere originally comes from Botswana and is on display in the German Gemstone Museum in Idar-Oberstein. A 224 kg sphere with a diameter of 54 cm was cut from an 800 kg blank. 

Decoration

Medieval Christians used bloodstone to engrave scenes of the Crucifixion, which led to the name "martyr's stone", given the red spots of iron oxide contained in the stone, which evoke droplets of blood, or the color of the setting sun, hence the name heliotrope given to the stone.

Czech Republic

Jasper (associated with amethyst), was used to make the ornamentation of facades or walls, as in the Chapel of Saint Wenceslas in Prague, or in the Church of the Holy Cross in Karlštejn.

Italy

The Medici 's passion for objects made of semi-precious stone (jasper, onyx, carnelian, amethyst, malachite, agate, marble, or lapis lazuli) led Grand Duke Ferdinando I de ' Medici to found, in Florence in 1588, the art manufactory specializing in the work of hard stones (Treasury of the Grand Dukes). From the end of the 16th century, the fashion for vases and furniture made of hard stone spread and the taste and technique of Florentine mosaics became established. The manufactory continued its activity for more than three centuries, and became the Museum of the Hard Stone Manufactory of Florence.

A bloodstone cup, from the workshop of the Milanese master lapidary, Gasparo Miseroni, (1518-1573), is on display at the Silver Museum, Pitti Palace, Florence.

France

A superb specimen of jasper, bearing the monogram "IRI", of the German Emperor Rudolf II, is exhibited at the Louvre Museum, Paris. The nave is the work (around 1608), of the Italian lapidary, Ottavio Miseroni, (1567 - 1624), in his workshops in Prague. It became (between 1653 and 1661), the largest vase in the collection of gems of King Louis XIV.

Russia

The master lapidaries of the three Imperial Lapidary Manufactories of Peterhof, Yekaterinburg, or of the Imperial Lapidary Manufactory of Kolyvan (ru), in Siberia , were accustomed to working on large art objects, using the technique of Russian mosaic (or Russian school of Florentine mosaic), by veneering thin strips of semi-precious stones such as malachite, rhodonite, lapis lazuli, skillfully assembled on works of art in bronze or stone. Jasper was also used to make ornamental bowls,. Many vases and art objects made of jasper, of different colors, are exhibited in the Hermitage Museum, in Saint Petersburg.

The famous Kolyvan Vase or "Tsarina of Vases", weighing 19.2 tons, is a symbol of the extreme professionalism of the Altai stonemasons and irrefutable proof of the unique wealth of this mountain range. The vase was designed by the architect Avraam Melnikov, who himself supervised the manufacture from 1831 to 1843. It is an extremely difficult process to work a five -meter block of "Resnev jasper" for more than eleven years. A monolithic block found in 1819 in the Revnyukha mountain , and extracted inFebruary 1829. This variety of stone is very hard, but at the same time fragile and unable to withstand shocks. The oval cup, 5 meters long and 3.25 meters wide, was cut at the Imperial Lapidary Manufactory in Kolyvan, then transported on a sleigh, pulled by 154 horses, to the Chusovaya River, to be transferred to a barge, and reach Saint Petersburg, inFebruary 1843. The vase bears a large number of retouches and patches, but they have been matched with such skill that they cannot be spotted. The work was completed in the New Hermitage, and kept packed on the Neva embankment. This is only theNovember 5, 1849, that the "Tsarina of Vases" was transported, thanks to a hole in a wall and displayed in the hall on a pedestal  built especially for her .

United States

Some polished jaspers develop surprising images, so much so that certain origins, such as those from Idaho, or Oregon, have received a separate name, such as Bruneau Jasper (or Bruneau jasper), or even Owyhee.

Manipulations and imitations

The variety of colors and patterns in jasper makes it easy to imitate using similar-looking rocks and varieties of other minerals. For example, the serpentine variety silvereye is also sold under the name zebra jasper. Flower jasper is actually unakite and is also a rock, like rhyolite, which is sold as leopard skin, rainforest, or eye jasper.

Criteria for discernment

Jasper is made of SiO 2 and therefore formed from chalcedony, very close to heliotrope but, above all, to agates.

It is distinguished from others by its infinite colors, its non-fluorescence, the fact that it does not contain detrital quartz, but above all because jasper contains 5 to 20% of something other than the original deposit.

Identification is all the more delicate as there is no objective criteria established between these three formations which all have the same origin. Many minerals will therefore remain contested or undeterminable, with the literature sometimes even contradictory on the subject.

If we are dealing with jaspers that are very rich in impurities, density can be the determining factor as long as the average density of the added materials is very different from that of quartz.

The banded or spotted formations are mostly agates and it is the opacity which will often be decisive in the identification.

Esotericism

Conrad Gessner, a famous naturalist in the late Middle Ages, wrote: "Jasper is a shield before the breast, a sword in the hand, and a snake beneath the feet. It protects against all illnesses and renews the spirit, heart, and mind." The ancient Greeks believed that jasper brought inner harmony to its wearer and that women who wore the stone would have a harmonious pregnancy. Red jasper was said to be the best remedy for nausea and excessive eating. In the Book of Nature written by Konrad von Megenberg in the 14th century (and adopted from it in the Speyer Women's Booklet of 1460), jasper is described as effective for weak labor.

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