Novaculite
Encyclopedia
Chert
Chert 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...
or flint
Flint
Flint 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...
found in the Ouachita Mountains
Ouachita Mountains
The Ouachita Mountains are a mountain range in west central Arkansas and southeastern Oklahoma. The range's subterranean roots may extend as far as central Texas, or beyond it to the current location of the Marathon Uplift. Along with the Ozark Mountains, the Ouachita Mountains form the U.S...
of Arkansas
Arkansas
Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...
and Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...
and in the Marathon Uplift
Marathon Uplift
The Marathon Uplift is a Tertiary-age domal uplift, approximately in diameter, in southwest Texas. The Marathon Basin was created by erosion of Cretaceous and younger strata from the crest of the uplift...
of Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
. Novaculite is considered to be highly siliceous sediments and may be a product of the low-grade metamorphism
Metamorphism
Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...
of chert beds. The strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
were deposited in the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
Period and subjected to uplift and folding during the Ouachita orogeny
Ouachita orogeny
The Ouachita orogeny was a mountain building event that resulted in the folding and faulting of strata currently exposed in the Ouachita Mountains...
of the Pennsylvanian
Pennsylvanian
The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...
/Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
Periods. Novaculite is very resistant to erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
and the layers of novaculite stand out as ridges in the Ouachita Mountains.
Novaculite is a form of microcrystalline or cryptocrystalline quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
. The color varies from white to grey-black and the specific gravity
Specific gravity
Specific 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...
shows an increase from 2.2 to 2.5. The very hard dense rock is used as a whetstone
Sharpening stone
Sharpening stones, water stones or whetstones are used to grind and hone the edges of steel tools and implements. Examples of items that may be sharpened with a sharpening stone include scissors, scythes, knives, razors and tools such as chisels, hand scrapers and plane blades...
. It has been mined since prehistoric times both as material for use as arrow and spear points and as sharpening stones. Moreover, the upper strata of Arkansas Novaculite, known as tripoli
Rotten stone
Rotten stone, sometimes spelled as rottenstone, also known as tripoli, is fine powdered rock used as a polishing abrasive in woodworking. It is usually weathered limestone mixed with diatomaceous, amorphous, or crystalline silica...
, has found a niche within the coatings, adhesives, sealants and elastomer industry as a performance additive or filler. Tripoli is mined just east of Hot Springs, Arkansas
Hot Springs, Arkansas
Hot Springs is the 10th most populous city in the U.S. state of Arkansas, the county seat of Garland County, and the principal city of the Hot Springs Metropolitan Statistical Area encompassing all of Garland County...
by Malvern Minerals Company.
The word novaculite is derived from the Latin
Latin
Latin 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...
word novacula, for razor stone.
External links
- Arkansas Geological Commission: Novaculite
- Babcock, L.L., Novaculite - The Arkansas Sharpening Stone