Novaculite

Novaculite (from Latin novacula = sharp knife, razor ) is a very fine-grained metamorphic rock pebbles. The material is mostly used for whetstones. It is best known as the Arkansas Washita stone or stone and is mined in this form in the United States.

And rock formation

Novaculite is a chert, and thus a hard, isotropic rock, from white to black gray color and sedimentary origin. It consists of cryptocrystalline quartz (silicon dioxide), subordinate to and from Chalcedon and small amounts of feldspar and garnet, and shows a conchoidal fracture with sharp edges. Novaculite as diatomaceous earth or flint is on a lake or ocean floor from the remains of organisms originated with silica skeletons, as they have diatoms, or other silica- rich residues, such as the needles of siliceous sponges. In the course of diagenesis, the silica was enriched by solute transport in nodules and layers. Unlike the flint novaculite a further structural change was defeated during a pressure- stressed metamorphosis, which led to a drastic Neukristallisierung which produced a fine, homogeneous microstructure.

Occurrence

Novaculite is mainly used in the Ouachita Mountains in Arkansas and Oklahoma in the United States. Here the parent rock outsourced from the Devonian, Carboniferous metamorphic rock formed by the a pressure- stressed metamorphosis during the formation of the Ouachita Mountains. Other reserves are found in Texas in Caballos Novaculite the Marathon Uplift.

Mining and using the

The rock is mined primarily in Arkansas in the counties of Garland and Hot Spring. Since it is very brittle, no blasting is to reduce used, it is cut with diamond saws and polished using abrasives such as silicon carbide.

The rock was used by native Americans in the arrow or spear points, due to its excellent properties. Today it is exclusively as a natural whetstone use.

Commercially, it is sold under the name Arkansas stone - extremely fine-grained, typically cloudy- white or light gray to black-gray, with a waxy luster - or Washita stone - similar to hard, slightly coarser in grain and often colored - sold. The stone is always with little paraffin or odorless lamp oil (hence the name ' stone oil ') for sharpening of knives, tools and surgical instruments used, the use of water very quickly leads to clogging of the surface and is therefore unsuitable. An exception is the rare milky white soft Arkansas, which is available in a slightly coarser form, where you need be able to work with water. There are many different variants Arkansas stone. They usually have a grain size of approximately 6000 to 8000 JIS and do not form an abrasive slurry ( 'Paste '). Since they are very hard, they are unlike other natural grindstones only a little wear and long hold the shape. In general, the black and glassy stones are denser than the white.