Jasper

Jasper- (from Greek ἴασπις the name means "spotted or speckled stone"), a micro cryptocrystalline rock, consist of mainly of quartz, chalcedony and pigmented impurities of other minerals (epidote, actinolite, clinkstone, mica, brassil, oxides and ferrum oxide and manganese), a semi-precious ornamental stone. The some breeds, which traditionally are classed as Jasper, include feldspar; it is either gray quartzo-feldspathic cherts or acidic effusives (porphyry). Among the breeds of Jasper, you can occur quartz-free, garnet-riched (up to 20% andradite). In ancient times glassy colored (mostly green color) chalcedony was classed as Jasper.

Elemental composition of Jasper is approximately as follows:

SiO2 80—95 %; Al2O3 and Fe2O3 to 15 %; CaO 3—6 %

The variety of Jasper has considerably in texture: massive, spotted, banded, brecciated, puckered and etc. The presence of many nonuniformity impurities provides variety and garishness of colouring. Sole-coloured Jasper is a rarity in nature.

In ancient times, Jasper was used as stamps or amulets to protect from dry period and vision problems. In these latter days Jasper is a popular material for art stone products, cabochons, stone mosaics. When you planishing and polishing require caution: ribbon jasper tends to disintegrate boundary layers. In the era of Catherine the Great Jasper was much sought after, the Queen built stone cutting manufacturers and some large factories for processing Jasper stones.


Varieties:

Depending on the color, pattern, deposit or consistence Jasper can be classified:

  • Agate-jasper;
  • Egyptian jasper («Nilotic chalcedony»);
  • Ribbon jasper (used for gemma);
  • Basanite (black fine-graded jasperlike effusive rock from North Carolina, USA, which is used as a touchstone for determining of alloy by color of line);
  • «Bloody jasper», Picture jasper (with landscape patterns);
  • Nunkirhenskaya jasper (dust-colour, close-grained; named after deposit of the Hunsrück, Germany);
  • Jasper painted Berlin blue, called the German or Swiss nitrate of silver, which is used as imitation of lasurite;
  • Plasma (deep-green, evenly-grained);
  • Prase (green jasper or ornamental stone of quartz group- green homogenous quartz);
  • Silex (with brown and red spots);
  • Irnimit (blue jasper, it has characteristic- blue crack s and spots in cherry, orange, gray jasperlike refuse stone).