Jasper

Jasper is an opaque, [ [http://www.mindat.org/min-2082.html Mindat: Jasper profile] ] impure variety of silica, usually red, yellow or brown in color. This mineral 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 at one time for snuff boxes. When the colors are in stripes or bands, it is called "striped" or "banded" jasper. Jaspilite is a banded iron formation rock that often has distinctive bands of jasper. Jasper is basically chert which owes its red color to iron(III) inclusions. The specific gravity of jasper is typically 2.5 to 2.9. [ [http://www.cst.cmich.edu/users/dietr1rv/jasper.htm R. V. Dietrich, "Gemrocks"] ]

Etymology and history

The name means "spotted or speckled stone", and is derived from Greek "iaspis", (feminine noun) [http://cf.blueletterbible.org/lang/lexicon/lexicon.cfm?Strongs=G2393&t=KJV ] via a Semitic language (cf. Hebrew "yashepheh", Akkadian "yashupu"), ultimately from Persian "yashp".

Green jasper was used to make bow drills in Mehrgarh between 4th-5th millennium BCE.Kulke, Hermann & Rothermund, Dietmar (2004). "A History of India". Routledge. 22. ISBN 0415329205.] Jasper is known to have been a favourite gem in the ancient world; its name can be traced back in Hebrew, Assyrian, Persian, Greek and Latin. [ [*http://www.gemstone.org/gem-by-gem/english/jasper.html International Colored Gemstoen Association: Jasper] ] On Minoan Crete within present day Greece jasper was carved to produce seals circa 1800 BC based upon archaeological recoveries at the palace of Knossos. [ [http://letmespeaktothedriver.com/site/10854/knossos.html#fieldnotes C. Michael Hogan, "Knossos fieldnotes", Modern Antiquarian (2007)] ]

The word "yashepheh" in the Masoretic text of Exodus 28:20, referring to a stone in the Hoshen, is thus reflected in the Septuagint by the word "Iaspis", and usually translated into English as "Jasper". Despite the most common form of Jasper being red, scholars think that the "yashepheh" here actually refers to a green form of Jasper - which was very rare, and so highly prized; the Greeks used "Iaspis" to refer to the green form, while the red form simply fell under the term "Sard" - which just means "red". Rebbenu Bachya argues that this stone represents the tribe of Benjamin, but there is actually a wide range of views among traditional sources about which tribe the stone refers to.

It is described in the Book of Revelation (21:11) as follows: "It shone with the glory of God, and its brilliance was like that of a very precious jewel, like a jasper, clear as crystal."

Types of jasper

Jasper can appear as an opaque rock of shades of red due to mineral impurities. Patterns can arise from the formation process and from flow patterns in the sediment or volcanic ash that was saturated with silica to form jasper, yielding bands or swirls in the rock.

Jasper may be permeated by dendritic minerals providing the appearance of vegetative growths. The jasper may have been fractured and/or distorted after formation, later rebonding into discontinuous patterns or filling with another material. Heat or environmental factors may have created surface rinds (such as varnish) or interior stresses leading to fracturing.

A brown jasper that occurs as nodules in the Libyan desert and in the Nile valley is known as Egyptian jasper or Egyptian pebble.

Picture jaspers simultaneously exhibit several of these variations (such as banding, flow patterns, dendrites or color variations) resulting in what appear to be scenes or images in a cut section. Spherical flow patterns produce a distinctive orbicular appearance. Complex mixes of impurities produce color variations. Healed fractures produce brecciated jasper. Examples of this can be seen at Llanddwyn Island.

Orbicular jasper or "leopard jasper" is usually an opaque combination of tan, gray, black or reddish-brown circles or 'spots' of color, hence its name.

ee also

* Carnelian
* Sard

References