1911 Encyclopædia Britannica/Jasper
|←Jason of Cyrene||1911 Encyclopædia Britannica, Volume 15
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JASPER, an opaque compact variety of quartz, variously coloured and often containing argillaceous matter. The colours are usually red, brown, yellow or green, and are due to admixture with compounds of iron, either oxides or silicates. Although the term jasper is now restricted to opaque quartz it is certain that the ancient jaspis or ἰάσπις was a stone of considerable translucency. The jasper of antiquity was in many cases distinctly green, for it is often compared with the emerald and other green objects. Jasper is referred to in the Niebelungenlied as being clear and green. Probably the jasper of the ancients included stones which would now be classed as chalcedony, and the emerald-like jasper may have been akin to our chrysoprase. The Hebrew word yashefeh may have designated a green jasper (cf. Assyrian yashpu). Professor Flinders Petrie has suggested that the odem, the first stone on the High Priest's breastplate, translated “sard,” was a red jasper, whilst tarshish, the tenth stone, may have been a yellow jasper (Hastings's Dict. Bible, 1902).
Many varieties of jasper are recognized. Riband jasper is a form in which the colours are disposed in bands, as in the well-known ornamental stone from Siberia, which shows a regular alternation of dark red and green stripes. Egyptian jasper is a brown jasper, occurring as nodules in the Lybian desert and in the Nile valley, and characterized by a zonal arrangement of light and dark shades of colour. Agate-jasper is a variety intermediate between true jasper and chalcedony. Basanite, lydite, or Lydian stone, is a velvet-black flinty jasper, used as a touchstone for testing the purity of precious metals by their streak. Porcelain jasper is a clay indurated by natural calcination. (F. W. R.*)