Jasper is a microcrystalline, fine-grained variety of the mineral quartz (SiO 2 ) and is closely related to chalcedony, which is always fibrous . The relationship is so close that there are even pieces in which granular and fibrous quartz materials have grown together.
Due to its polycrystalline structure, jasper is generally opaque white and, through admixtures such as various iron oxides, can take on all hues from yellow to red and brown to black, but also pink and greenish hues.
Jasper is only processed into gemstones , which are very resistant to mechanical stress due to the Mohs hardness of 6.5 to 7. When ground and polished, the stone surfaces then have a shine similar to glass or grease .
Etymology and history
The word "jasper" is derived from the Latin iaspis from the Greek ἴασπις , íaspis for "speckled stone". This name, in turn, originally comes from an oriental language, possibly from ancient Egyptian or Persian ( yashp ). In Hebrew it is called Jaspheh . Jasper is the only gemstone name in the Nibelungenlied : there, a grass-green jasper adorns Siegfried's sword Balmung (verse 1783).
Jasper is very rarely found in its pure form. By adhesions with agate and opal , but also by foreign admixtures of up to 20% as aluminum oxide , iron oxide , iron hydroxide and manganese its chemical and physical properties vary greatly. Since the amount and distribution of these admixtures determine the appearance, the color and variety of the jasper is extremely large. In addition, the line color changes depending on the admixture and can hardly be used for authenticity testing.
As a result, many similarly shaped and grained minerals or varieties and even rocks whose color and pattern resemble those of jasper are sold under this name in the trade.
The names or trade names of the many varieties often reflect their place of origin, but also their color and design.
- The agate jasper (also jasper agate ) is a yellow, brown and green striped intergrowth of jasper and agate, strictly speaking a rock .
- The Egyptian jasper or ball jasper , Nile pebbles or jasper bulbs , is ocher yellow to brown and brick red, often striped and flamed and is found in large quantities as pebbles in the Nile and in the desert. Near Cairo it forms a conglomerate that probably belongs to the chalk formation .
- Due to its gray, green, yellow, red and brown colored, parallel striped or banded structure, the ribbon jasper is predestined for processing into gems .
- The fine-grained, black basanite is mainly known to jewelers and goldsmiths, because they use it as a sample.
- The picture jasper with brown and black grain is often confused with mookaite , epidote , pietersite , stromatolite , tiger iron because of its many facets . The picture jasper is mainly mined in South Africa , Oregon , Australia .
- The Dalmatian jasper is a variety with a gray to beige body and black speckles, which owes its name to the dog breed of the same name .
- Chert , which is often used as a synonym for jasper , is also fine-grained, but gray to red-brown, rarely green to black .
- The cellar forest agate (found in Kellerwald / North Hesse) is a white-veined red jasper.
- The landscape jasper, which is often imitated by similar looking rocks, shows lively patterns on the surface that can be interpreted as stylized landscapes or plants with little imagination. The brown color brought about by the addition of iron does the rest to reinforce this impression.
- As Mookait is a pink referred to pale red variety with cloud-like banded structure which predominantly in Australia is degraded.
- An after its place Nunkirchen named, white or yellowish gray to brownish red variety under the name Nunkirchner Jasper known. It is often colored with Berlin blue and sold as an imitation of lapis lazuli under the trade names Deutscher Lapis , Swiss Lapis or Nunkirchener Lapis Lazuli .
- Ocean jasper comes from the Marovato mine in Madagascar, which has been known since 2001. In esotericism it is also marketed under the names eye jasper or agate as well as spherical rhyolite or chalcedony.
- Porcelain jasper (also Porzellanit ) is the name that is no longer used for various rocks that were created from clay or sandstone under high temperatures and at the same time low pressures. They are often found as contact metamorphoses on basalt chimneys or coal seams, where they were formed during seam fires. Find locations are, for example, Epterode near Großalmerode in Hessen ( Jasper von Bühlchen ), or Planitz near Zwickau. Although there is sometimes an outward resemblance to jasper (bright colors and sometimes - with a high glass content - shell-like breakage), these rocks have nothing to do with jasper in the mineralogical sense. The correct name is fritted rock or buchite .
- The misleading, but still used term Prasem stands for a fine-grained, washed-out green jasper variety on the one hand, but also for a leek-green quartz aggregate on the other.
- Plasma is very similar to Prasem, but has a rather coarse-grained structure, so that its green color looks dirty.
- Silex is the yellow and red-brown spotted or concentrically striped variety called, mostly red and brown, also yellowish and black, can be found in many places, especially on iron stone entrances.
- Indian zebra jasper is dark brown with light brown streaks and often contains fossilized shells and snails.
The heliotrope is often wrongly assigned the synonym blood jasper , but it is an independent quartz variety of leek green color with pink to red spots. In contrast to the granular jasper, however, heliotrope has a radial structure, but can look similar to the jasper by forming spherical aggregates.
Colorfully banded and speckled jasper from Madagascar
Dalmatian jasper, rough stone and smooth touch as Trommelstein
Mookaite (pink) with black, dendritic mineral inclusions
Education and Locations
Jasper is found coarse, sprinkled, in balls and attachments, usually as a duct filling or tubers, rarely also in grape or kidney-shaped shapes.
In addition to the sites already mentioned for the varieties, jasper is also found in the following places: Ore Mountains , Harz , Auggen , Kleinkems and Istein near Efringen-Kirchen as well as Idar-Oberstein in Germany , Yekaterinburg and Okhotsk in Siberia , on the Italian island of Sicily and the French island of Corsica , as well as in Tyrol .
Use as a gem stone
In ancient times, jasper was a highly regarded gemstone among the Greeks and Romans .
The Bible says of the heavenly Jerusalem revealed to the apostle John :
“The foundation stones of the city wall are adorned with precious stones of all kinds; 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 beryl , the ninth a topaz , the tenth a Chrysoprase , the eleventh a hyacinth and the twelfth an amethyst . "
Over the centuries, the jasper has lost its importance and appreciation and is currently used for sealing stones , boxes, vases , table tops, jugs, mosaics, architectural works, etc.
- The largest polished green jasper is located as a profiled bowl in the Hermitage in Saint Petersburg with a size of 5.04 × 3.22 meters. The bowl made of Revnev jasper from the Altai , also known as the Kolyvan vase , has a weight of around 19 tons, a circumference of around 12.7 meters and a height of around 2.57 meters.
- Another cut red jasper was made from a 2850 kg blank into a ball weighing about one ton and a diameter of 87.5 cm. It is located in Sankt Augustin - Hangelar .
- Another large jasper ball originally comes from Botswana and is in the German Gemstone Museum in Idar-Oberstein . A 224 kg ball with a diameter of 54 cm was ground from an 800 kg blank.
Manipulations and imitations
The variety of colors and patterns in jasper makes it easy to imitate it using similar looking rocks and varieties of other minerals. For example, the serpentine variety Silberauge is sold under the name Zebra-Jasper . Flower jasper is actually unakite and is just as much a rock as rhyolite, which is sold as leopard skin , rainforest or eye jasper .
The natural scientist Conrad Gessner, famous in the late Middle Ages, said: “The jasper is a shield in front of the chest, the sword in the hand and the snake under the feet. It protects against all illnesses and renews spirit, heart and mind. ”The ancient Greeks believed that the jasper gave its wearer inner harmony and that women have a harmonious pregnancy by wearing the stone. The red jasper should best help with nausea and excessive appetite.
- Petr Korbel, Milan Novák: Mineral Encyclopedia (= Villager Nature ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 88.92 .
- Martin Okrusch, Siegfried Matthes: Mineralogy. An introduction to special mineralogy, petrology and geology . 7th, completely revised and updated edition. Springer, Berlin [a. a.] 2005, ISBN 3-540-23812-3 , pp. 114 .
- Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th, revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 162-163 .
- Bernhard Bruder: Beautified stones. Recognizing imitations and manipulations in gemstones and minerals . Neue Erde, Saarbrücken 2005, ISBN 3-89060-079-4 , p. 76 .
- Mineral Atlas: Jasper (Wiki)
- Jasper MinDat (English)
- Knowledge on the Net - Hildegard von Bingen to Jasper
- ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th, revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 162 .
- ↑ Hermann Tertsch: The secret of the crystal world. Novel of a science . Gerlach & Wiedling, Vienna 1947, p. 100 .
- ↑ Porcelain jasper in the gemstone dictionary of the Vienna Gemstone Center
- ↑ Mineralienatlas: Porzellanit
- ↑ The Kolyvan vase, the largest polished jasper gemstone weighing around 19 tons
- ↑ Largest ball made of red jasper weighing 1 ton
- ↑ did you know . In: Berliner Zeitung , May 13, 1995