
Biggs jasper is a variety of the mineral
jasper
Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to ...
. It is a "picture jasper" – a jasper that exhibits particular patterns and colors – and is used as an opaque
gemstone
A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...
.
It exhibits intricate, shell- or layer-like patterns in shades of brown ranging from beige to dark brown.
The stone was first discovered around 1960 near
Biggs Junction, Oregon
Biggs Junction is an unincorporated community and census-designated place (CDP) in Sherman County, Oregon, United States.
Biggs Junction is located on the south side of the Columbia River at the junction of Interstate 84/ U.S. 30 and U.S. 97 ...
, and is found in the
basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
deposits of the American
Pacific Northwest
The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...
. Biggs jasper was formed as
mud
Mud (, or Middle Dutch) is loam, silt or clay mixed with water. Mud is usually formed after rainfall or near water sources. Ancient mud deposits hardened over geological time to form sedimentary rock such as shale or mudstone (generally cal ...
from volcanic ash was deposited on basalt terrain, and subsequently heated and compressed through volcanic activity.
Because of this
sedimentary
Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...
origin, it is relatively rare, and is valued as a gemstone.
[
]
Discovery
Biggs jasper was first found around 1960 at the bottom of a creek near Biggs Junction, Oregon
Biggs Junction is an unincorporated community and census-designated place (CDP) in Sherman County, Oregon, United States.
Biggs Junction is located on the south side of the Columbia River at the junction of Interstate 84/ U.S. 30 and U.S. 97 ...
, after possibly being carried some distance by water from the outcrop where it originated. More of the stone was found in the 1960s, particularly during road works in 1966 when U.S. Route 97 was relocated through a canyon south of Biggs Junction. Road workers found the jasper in a rock cut, collected it and sold it to rock shops. This brought the attractive stone to the attention of collectors, who began to search for it around Biggs Junction.[
]
Geology
Biggs jasper is found between two of the basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
flows that once covered the U.S. states of Oregon
Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...
, Washington
Washington most commonly refers to:
* George Washington (1732–1799), the first president of the United States
* Washington (state), a state in the Pacific Northwest of the United States
* Washington, D.C., the capital of the United States
** A ...
and parts of Idaho
Idaho ( ) is a landlocked U.S. state, state in the Pacific Northwest and Mountain states, Mountain West subregions of the Western United States. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington (state), ...
. Many thousands of years passed between the individual flows, allowing life to flourish. During this time, the volcanic ash decomposed into clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...
and was deposited by rain water in streams and lakes atop the cooled basalt. There it mixed with silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...
and iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
from the weathering
Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...
of the then-recent igneous rock
Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.
The magma can be derived from partial ...
s, forming a plastic colloid
A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others exte ...
.[
When lava next flowed over it, the heat and pressure transformed the muddy mixture. As water escaped it in the form of superheated steam, pressure variations resulted in flexing and many short fluctuating changes, reflected in the jasper's many thin, parallel bands.][ The hydrothermal reaction progressed as a shock wave through the mud, removing iron from it and depositing the iron as intertwining bands of ]limonite
Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as , although this is not entirely accurate as the ratio of oxide to hydroxide can vary qu ...
. The altered rock remained plastic
Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...
, and subject to local movement as a result of pressure changes. These caused the great variety of marbled, rosette
Rosette is the French diminutive of ''rose''. It may refer to:
Flower shaped designs
* Rosette (award), a mark awarded by an organisation
* Rosette (design), a small flower design
*hence, various flower-shaped or rotational symmetric forms:
** R ...
-like and picture designs found in Biggs jasper.[
Near Biggs jasper a ]stratum
In geology and related fields, a stratum (: strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ...
of white clay is sometimes found, locally named "wascoite" for the town of Wasco, Oregon
Wasco is a city in Sherman County, Oregon, United States. The population was 410 at the 2010 census.
Geography
According to the United States Census Bureau, the city has a total area of , all land.
Wascoite or Biggs jasper, a type of white ...
. It is probably the end form of much-weathered volcanic debris. Also often found together with Biggs jasper is a dark gray, somewhat translucent
In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable light scattering by particles, scattering of light. On a macroscopic scale ...
chert
Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...
. It formed from colloidal silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...
released from the volcanic debris. Because of their different physical properties, water movement separated the two colloids from which the chert and Biggs jasper resulted from each other, so that both were deposited in nearly pure form.[
]
Use
Biggs jasper is used as a gemstone in bolo tie
A bolo tie (sometimes bola tie or shoestring necktie) is a type of necktie consisting of a piece of cord or braided leather with decorative metal tips (called aiguillettes) and secured with an ornamental clasp or slide.
Popularity
In the United ...
stones, necklaces, bracelets, brooches and other jewelry. It is also of interest to mineral collectors, who sometimes cut slabs of it to resemble landscapes beneath a realistic-looking sky.[
]
References
{{reflist, 25em
Jasper
Geology of Oregon