Sharpening history. Atlyanski slate

Atlyanski slate is one of the popular natural abrasives in the Sovjet time. It was extracted at the Atlyansk deposit of roofing slate near the city of Mias, Chelyabinsk region, in the rural area called Syrostan. The stone was a type of black slate mined in the Ural mountains and was used mainly for making souvenirs and chalkboards for schools. From 1930, the "Sverdkhimles" trust and the Syrostan artel "Zavety Lenina", part of it, carried out industrial slate mining near Podyachnaya mountain. Several surface quarries, three mines, and one adit were exploited. In total, three types of raw materials were extracted: gray-blue slate, which was used for making chalkboards, and black and gray slates, which were used for making honing and sharpening stones. Work on the Atlyansk deposit was discontinued many years ago and to date, there are neither mines nor quarries. However, produced by the artel "Zavety Lenin" razor and tool honing stones are still used by some sharpening enthusiasts.

Geologically, the Atlyansk slate is a type of metamorphosed clay-slate. This is a hard clay rock of slate composition, not soaking in water. It is formed during recrystallization of argillites (hard rocks formed during the compression of clays), at the last stage of lithogenesis, at temperatures of 200-350 °C and high pressures, at depths from 6 to 11 km. By their composition, they are highly compacted clay. Slate is formed from very fine particles of various clay minerals (kaolinite, sericite, chlorite, talc, gumbelite, pyrophyllite, and other substances). Clay slate also includes fragments of quartz, feldspar, mica, etc. It is these inclusions that make it possible to sort the slate according to the degree of suitability for sharpening. The fewer inclusions a particular stone has, the more evenly it works and leaves fewer parasitic marks. The slates of the Ural deposits have a fine-grained structure with completely lost primary textures and structures. They have such characteristics as low water absorption, high resistance to weathering, and fracture strength (perpendicular to slate). However, they contain quite large inclusions of pyrite. 

Pencil slates, which include Atlyanski slate, are black rocks, quite brittle, easily split into thin smooth plates. At the same time, they have a fairly soft structure, which manifests itself in sharpening. 

One of the characteristic properties of slate can be called the exact match of the color and qualities of the stone.  The darker the rock, the deeper it was embedded in the rock and the denser its structure. Thus, the lightest stones are the softest, and the darkest are the hardest. The Atlyanski slate has a color palette from completely black stone to dark gray. Often there are color irregularities in the form of dark or light stripes and light spots. The average density of the stone is about 2.70 g/cm. When the stone was put on sale, it was divided into two types: honing stone for tool – for finishing of knives and tools and honing stone for razors - whetstone for finishing of razors. The razor honing stone is more delicate to work with and leaves fewer parasitic marks. The grain size (gritness of the stone) is approximately defined as 4000-6000 according to JIS for tool honing stone and slightly larger for a razor. Altyanski slate is a water stone, however, it does not need soaking, but only surface spraying. Leveling of the uneven surface of the stone can be carried out on a silicon carbide powder and a fast preparation for work on its own suspension. The suspension of the stone is dark gray.  

In the work, slate manifests itself as a finishing stone of medium abrasiveness, works softer than English Charnley Forest slate or Chinese Guangxi stone. Marks after this stone are in the range of 1-2 microns. It doesn't work very fast and doesn't have aggression. It is particularly good for carbon steels of low hardness. 

The Atlyanski slate was used in Russia and the USSR for a long time and still, it can be found on sharpening flea markets and in collections of sharpeners. Just like the belorechit stone, it is gradually becoming a part of the sharpening history.