Jasper, Picasso

Mineralogy of Picasso Jasper

Mineral Family: Tectosilicate

Chemical Composition: SiO₂ 
Cleavage: None
Color: Red, white, yellow, brown and black
Crystal System: Hexagonal/Trigonal
Form/Habit: Cryptocrystalline
Fracture: Conchoidal
Gravity: 2.58-2.91
Hardness: 6.5-7
Luminescence: None
Luster: Vitreous
Streak: White
Transparency: Translucent to Opaque

Location: Jasper is found throughout the world. The most notable deposits are found in Australia, Brazil, Canada, Egypt, India, Kazakhstan, Madagascar, Russia, South Africa, the United States, and Uruguay.  “Picasso” Red Jasper is from a small deposit in Peru.

Mineral Family: True Jasper is a Silicate mineral. However, “jasper” is a term that is often used to describe any spotted stone. As such many varieties of spotted Rhyolite, a type of igneous rock, are misrepresented as jaspers. For example, “Ocean Jasper” or “Leopardskin Jasper” are both igneous rocks rather than true Jaspers.  From a geological point of view, only spotted microcrystalline Quartz may be properly referred to as Jasper. True Jasper is a tiny twig on a far off branch of the crystal tree, scientifically it is a “subdivision of a subdivision of a subdivision, of a subdivision of a subdivision!” Silicate minerals form the largest family of minerals, including more than 25% of all known minerals and 40% of all common minerals. In addition to being a major part of the Earth’s crust, Silicate minerals have also been found on the moon and in meteorites. Silicates are minerals which contain the elements Silicon (a light gray shiny metal) and Oxygen (a colorless gas). Together, these two elements form a tetrahedra – a shape similar to a pyramid – with a Silicon atom in the center and Oxygen atoms at each of the three corners. These tetrahedras connect with other chemical structures, in six different ways, to form various minerals and rocks. There are six main groups of Silicate minerals, and these main groups are further subdivided into secondary subdivisions, such as Quartz and Feldspar.  Quartz is a large mineral family in its own right, and has two main subdivisions, macrocrystalline (crystals that are large enough to be seen by the naked eye, for example, Amethyst) and microcrystalline (crystals so small they can only be seen through a microscope, for example Agate). All microcrystalline Quartz fall under the subcategory of Chalcedony, which is then further subdivided. One of these categories is Jasper.

Formation: True Jasper is opaque Quartz with numerous inclusions. Clear Quartz  forms when silica acid solidifies in igneous rocks. Jasper, by contrast, forms when silica acid penetrates clay or sand, and solidifies in sedimentary rocks. Where the silica acid cools it hardens into Quartz, but with the addition of millions of tiny particles of sand, clay, and other minerals. These inclusions give Jasper their brilliant colors and random markings.  Picasso Jasper is a wonderful example of true Jasper, its various colors and markings each signify a different foreign inclusion.

Mining: Jasper is typically mined from the primary deposits which still have their original relationship with the host rock.

Enhancements: All Jaspers are natural, enhanced only by tumbling, cutting, and polishing.

Map courtesy of TravelBlog
Photos: Rough Red Jasper