Arkansas is considered one of the best natural stones for finishing the cutting edge of knives and other tools after basic sharpening. Arkansas is essentially a specimen of crystalline silica (fine-grained quartz, microquartzite) consisting of interlocking crystalline grains ranging in size from 1 to 6 microns. It is usually white, bluish or yellowish in color, with a waxy luster and a shell fracture. However, there is also a black variety of this mineral. as well as several gray ones with spots and streaks. Arkansas is one of the purest quartz rocks with SiO2 content within 99.5%. The remaining impurities, contain minor amounts of aluminum (0.02%), boron (0.0005%), calcium (0.03%), magnesium (0.05%), and manganese (0.0007%). In terms of foreign matter, Arkansas is purer than rock crystal. It is also characterized by very strong bonds between the grains, which form a homogeneous structure that ensures clean sharpening. Arkansas stones are divided into four types according to their hardness: Arkansas Soft, Hard Arkansas, Black Arkansas, Translucent Arkansas.
Arkansas Soft is a gray stone with dark “veins”. It is a microquartzite (novaculite) rock. It works effectively on most steels. Characterized by high grain uniformity and cleanliness of work.600-700 grit (according to JIS system) Used for basic and pre-finishing sharpening.
Hard Arkansas (geologic species – novoculite) – comes in a variety of shades and colors. Type of work is pre-finish sharpening. The grain size for natural stones is approximately JIS 2000. Grain hardness is high. Works with oil, does not require soaking.
Black Arkansas – has color shades ranging from dark gray, to black. Stone for finishing. Grain size for natural stones is approximately JIS 3000 – 5000. Works with oil, does not require soaking. The structure of the stone is very dense, microcrystalline.
Translucent Arkansas (Translucent Arkansas) – comes in a variety of shades from light gray to white with a yellowish tint. The type of work is finish finishing. The grain size for natural stones is approximately JIS 4000 – 6000. Works with oil, does not require pre-soaking. The structure of the stone is very dense.
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When sharpening knives, Arkansas stones densify the structure of the metal, this is especially evident with prolonged use and the longer it is, the more pronounced the effect. It is noticeable first of all on carbon steels with hardness below 58 units on the Rockwell scale. The so-called “nagarting” occurs, the steel at the point of machining receives an increase in wear resistance. This effect is considered controversial in the sharpening community and is not scientifically proven. However, in practice, when using a knife, the increase in sharpness retention time after micro-quartzite treatment is very noticeable. On harder steels “nagartovka” is less pronounced and does not give a significant increase.
Arkansas stones show good results and when working with polishing pastes based on aluminum oxide, for example, paste Luxor. Paste, applied to the oiled surface of the stone allows you to spend less time on sharpening, increasing the speed of metal removal. And given the extremely low, almost imperceptible rate of wear of this abrasive, it becomes virtually “eternal” lapping, with excellent retention of the plane of the working surface, without the formation of workings. Arkansas stones give a premium level of sharpness and at the same time can work for many years, passing on the inheritance to a new generation of sharpeners.