Jasper, a form of
chalcedonyChalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of the minerals quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic...
, is an
opaqueOpacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc...
, impure variety of
silicaThe chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
, usually
redRed is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...
,
yellowYellow is the color evoked by light that stimulates both the L and M cone cells of the retina about equally, with no significant stimulation of the S cone cells. Light with a wavelength of 570–590 nm is yellow, as is light with a suitable mixture of red and green...
,
brownBrown is a color term, denoting a range of composite colors produced by a mixture of orange, red, rose, or yellow with black or gray. The term is from Old English brún, in origin for any dusky or dark shade of color....
or
greenGreen is a color, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 520–570 nanometres. In the subtractive color system, it is not a primary color, but is created out of a mixture of yellow and blue, or yellow and cyan; it is considered...
in color; and rarely
blueBlue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm. It is considered one of the additive primary colours. On the HSV Colour Wheel, the complement of blue is yellow; that is, a colour corresponding to an equal...
. This
mineralA mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
breaks with a smooth surface, and is used for ornamentation or as a
gemstoneA gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...
. 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 formationBanded iron formations are distinctive units of sedimentary rock that are almost always of Precambrian age. A typical BIF consists of repeated, thin layers of iron oxides, either magnetite or hematite , alternating with bands of iron-poor shale and chert...
rock that often has distinctive bands of jasper. Jasper is basically
chertChert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...
which owes its red color to iron(III)
inclusionsIn mineralogy, an inclusion is any material that is trapped inside a mineral during its formation.In gemology, an inclusion is a characteristic enclosed within a gemstone, or reaching its surface from the interior....
. The
specific gravitySpecific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
of jasper is typically 2.5 to 2.9. The jasper is, along with
Heliotrope (bloodstone)The mineral heliotrope, also known as bloodstone, is a form of chalcedony . The "classic" bloodstone is green chalcedony with red inclusions of iron oxide or red jasper...
, one of the traditional birthstones for March. It is also a stone in the Jewish
High PriestThe High Priest was the chief religious official of Israelite religion and of classical Judaism from the rise of the Israelite nation until the destruction of the Second Temple of Jerusalem...
's
breastplateThe priestly breastplate was a sacred breastplate worn by the High Priest for the Israelites, according to the Book of Exodus...
, described in Exodus 28.
Etymology and history
The name means "spotted or speckled stone", and is derived via Old French
jaspre (variant of
Anglo-NormanAnglo-Norman is the name traditionally given to the kind of Old Norman used in England and to some extent elsewhere in the British Isles during the Anglo-Norman period....
jaspe) and Latin
iaspidem (nom.
iaspis)) from
GreekGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
ἴασπις
iaspis, (feminine noun) from a
Semitic languageThe Semitic languages are a group of related languages whose living representatives are spoken by more than 270 million people across much of the Middle East, North Africa and the Horn of Africa...
(cf.
HebrewHebrew is a Semitic language of the Afroasiatic language family. Culturally, is it considered by Jews and other religious groups as the language of the Jewish people, though other Jewish languages had originated among diaspora Jews, and the Hebrew language is also used by non-Jewish groups, such...
יושפה
yushphah,
AkkadianAkkadian is an extinct Semitic language that was spoken in ancient Mesopotamia. The earliest attested Semitic language, it used the cuneiform writing system derived ultimately from ancient Sumerian, an unrelated language isolate...
yashupu), ultimately from
PersianPersian is an Iranian language within the Indo-Iranian branch of the Indo-European languages. It is primarily spoken in Iran, Afghanistan, Tajikistan and countries which historically came under Persian influence...
یشپ
yašp.
Green jasper was used to make
bow drillThe bow drill is an ancient tool. While it was usually used to make fire, it was also used for primitive woodworking and dentistry. It consists of a bearing block or handhold, a spindle or drill, a hearth or fireboard, and a simple bow...
s in
MehrgarhMehrgarh , one of the most important Neolithic sites in archaeology, lies on the "Kachi plain" of Balochistan, Pakistan...
between 4th-5th millennium BC. Jasper is known to have been a favorite gem in the ancient world; its name can be traced back in
ArabicArabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
,
PersianPersian is an Iranian language within the Indo-Iranian branch of the Indo-European languages. It is primarily spoken in Iran, Afghanistan, Tajikistan and countries which historically came under Persian influence...
,
HebrewHebrew is a Semitic language of the Afroasiatic language family. Culturally, is it considered by Jews and other religious groups as the language of the Jewish people, though other Jewish languages had originated among diaspora Jews, and the Hebrew language is also used by non-Jewish groups, such...
,
AssyrianAkkadian is an extinct Semitic language that was spoken in ancient Mesopotamia. The earliest attested Semitic language, it used the cuneiform writing system derived ultimately from ancient Sumerian, an unrelated language isolate...
, Greek and
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
. On
MinoanThe Minoan civilization was a Bronze Age civilization that arose on the island of Crete and flourished from approximately the 27th century BC to the 15th century BC. It was rediscovered at the beginning of the 20th century through the work of the British archaeologist Arthur Evans...
CreteCrete is the largest and most populous of the Greek islands, the fifth largest island in the Mediterranean Sea, and one of the thirteen administrative regions of Greece. It forms a significant part of the economy and cultural heritage of Greece while retaining its own local cultural traits...
within present day
GreeceGreece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
jasper was carved to produce seals circa 1800 BC, as evidenced by archaeological recoveries at the
palaceA palace is a grand residence, especially a royal residence or the home of a head of state or some other high-ranking dignitary, such as a bishop or archbishop. The word itself is derived from the Latin name Palātium, for Palatine Hill, one of the seven hills in Rome. In many parts of Europe, the...
of
KnossosKnossos , also known as Labyrinth, or Knossos Palace, is the largest Bronze Age archaeological site on Crete and probably the ceremonial and political centre of the Minoan civilization and culture. The palace appears as a maze of workrooms, living spaces, and store rooms close to a central square...
.
Types
Jasper is an
opaqueOpacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc...
rock of virtually any color stemming from the mineral content of the original sediments or ash. Patterns arise during the consolidation process forming flow and depositional patterns in the original silica rich
sedimentSediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
or
volcanic ashVolcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
.
Hydrothermal circulationHydrothermal circulation in its most general sense is the circulation of hot water; 'hydros' in the Greek meaning water and 'thermos' meaning heat. Hydrothermal circulation occurs most often in the vicinity of sources of heat within the Earth's crust...
is generally thought to be required in the formation of jasper.
Jasper can be modified by the diffusion of minerals along discontinuities providing the appearance of vegetative growth, i.e.,
dendriticA crystal dendrite is a crystal that develops with a typical multi-branching tree-like form. Dendritic crystal growth is very common and illustrated by snowflake formation and frost patterns on a window. Dendritic crystallization forms a natural fractal pattern...
. The original materials are often fractured and/or distorted, after deposition, into myriad beautiful patterns which are to be later filled with other colorful minerals. Weathering, with time, will create intensely colored superficial rinds.
The classification and naming of jasper presents a challenge. Terms attributed to various well-defined materials includes the geographic locality where it is found, sometimes quite restricted such as "Bruneau" (a canyon) and "Lahontan" (a lake), rivers and even individual mountains, many are fanciful such as "Forest Fire" or "Rainbow", while others are descriptive such as "Autumn", "Porcelain" or "Dalmatian". A few are designated by the country of origin such as a Brown Egyptian or Red African leaving tremendous latitude as to what is called what.
Picture jaspers exhibit combinations of patterns (such as banding from flow or depositional patterns (from water or wind), dendritic or color variations) resulting in what appear to be scenes or images, on a cut section. Diffusion from a center produces a distinctive
orbicularOrbicular jasper is a variety of jasper which contains variably-colored orbs or spherical inclusions or zones. In highly silicified rhyolite or tuff, quartz and feldspar crystallize in radial aggregates of needle-like crystals which provide the basis or seed for the orbicular structure seen in this...
appearance, i.e., Leopard Skin Jasper, or linear banding from a fracture as seen in Leisegang Jasper. Healed, fragmented rock produces
brecciaBreccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
ted (broken) jasper. Examples of this can be seen at
Llanddwyn IslandYnys Llanddwyn or Llanddwyn Island is a small tidal island off the west coast of Anglesey, North Wales. The nearest town is Newborough.-Geology and geography:...
in Wales.
The term
basanite has occasionally been used to refer to a variety of jasper, for example a black
flintFlint is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. Inside the nodule, flint is usually dark grey, black, green, white, or brown in colour, and...
y or
chertyChert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...
jasper found in several New England states of the USA. Such varieties of jasper are also informally known as
Lydian stone or
lydite and have been used as touchstones in testing the purity of
precious metalA precious metal is a rare, naturally occurring metallic chemical element of high economic value.Chemically, the precious metals are less reactive than most elements, have high lustre, are softer or more ductile, and have higher melting points than other metals...
alloyAn alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
s.