Jasper | Type of Chalcedony
Jasper Stone Facts and Photos
Jasper which is well known in the world of rocks and minerals is a type of chalcedony that's a cryptocrystalline variety of quartz. Cryptocrystalline means that its crystals are too small to be seen with the naked eye. Although often referred to as a mineral it is in fact a rock because although made up primarily of quartz and/or chalcedony, it also features traces of many other minerals and substances. As well as being the reason why jasper is usually opaque the impurities are also responsible for the many different colours and markings that can be seen in the stone. In its purest form the mineral quartz is colourless and translucent to some degree but with the addition of other materials and/or minerals that changes. The presence of hematite which is iron causes jasper to turn red, clay causes a yellowish, white or grey colour and goethite usually results in yellow or brown varieties. Stones often exhibit more than one colour and whilst blue is rare, shades of red, yellow and brown are most common although many other colours are also possible.
Jasper begins to form when sediments become stuck together which happens when groundwater containing silica seeps through sedimentary rocks and subsequently dries up. It acts like a glue and cements everything together. The sediment helps determine the colours that will ultimately be present and patterns are often the result of the motion of the natural forces which brought the sediment or volcanic ash together.
Well known for occurring in many different colours and with a wide variety of patterns or markings, jasper is almost always opaque. Identification is sometimes made slightly easier because the first part of the name will often but not always offer a clue to a specific characteristic or the locality where the stone originated. Dalmatian, leopardskin and zebra jasper all exhibit characteristics that resemble the respective animals whilst red jasper is named for its colour which is caused by inclusions of hematite. Landscape, scenic and picture jasper are all types of mudstone and mookaite is named after the location in Western Australia where it's found. There are hundreds of different names but many including noreena, polychrome, poppy and imperial to name just a few offer little or no clue at all about the origins or characteristics of the stone.
Jasper is mostly used as a lapidary material and being opaque tends to be cut as a cabochon. It's relatively hard hence grades 6½ to 7 on Mohs scale of mineral hardness and can be found in most countries around the world. Tumbled stones are popular and widely used in alternative therapies such as crystal healing.
Red jasper veined with quartz. Photo - Stone Mania ©
A Little History
Although known for thousands of years the stone that was referred to as jasper by ancient writers such as Theophrastus (c.371 - c.287 BC), Pliny the Elder (23 - 79 AD) and others was not the same stone as we know today as jasper. In ancient times it was mostly described as being translucent, some wrote that it may also be cloudy and it was usually associated with "smaragdos" which is known today as emerald. Although documented as being green some writers including Pliny state that it also occurred in blue, purple, pink and some varieties were colourless.
It's widely believed that jasper or iaspis as it was once known was probably a generic name for translucent or transparent varieties of quartz that were not known by any other name. There are however indications that the mineral fluorite and jade may also have been included in this group because it was once common for rocks and minerals to be grouped according to their colour. The stone referred to as pink jasper is likely to have been rose quartz, blue would have been a type of chalcedony, green chrysoprase and stones which exhibited hues of brown were probably smoky quartz. All of these materials were widely used as seals which has enabled historians to identify them correctly.
The history of jasper cam be traced back thousands of years and is known to have been used in jewellery, for ornaments and many other purposes. There are references to it in Greek, Hebrew, Assyrian and Latin literature and in the Bible (Exodus 28.20), it's identified as being one of the gemstones in the High Priest's breastplate. Iaspis as it was known at that time is believed to have been the third stone in the fourth row of this religious garment.
Varieties in Our Collection
- Bumble Bee
- Landscape, Picture , Scenic (varieties of mudstone)
- Mookaite (Australian Jasper)
- Willow Creek
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Further ReadingInformation from Wikipedia
Jasper Agate or Chalcedony?