Thread: Translucent Arkansas stone?

Arkansas stones (novaculite) are a type of rock consisting primarily of silica. Other silica based rocks are obsidian, an igneous rock also called volcanic glass, Quartz a crystalized silica, sandstone which is a sedimentary rock, and chert which is a metamorphic rock. Novaculite is a type of chert.

Silica-based abrasives are not very aggressive in sharpening hardened steel such as razors. A hardened steel file has a hardness similar to that of a quartz crystal (about 6.5 on the Mohs scale). A steel file can scratch amorphous silica glass. Razors are not quite as hard as a hardened steel file, but some razors come close.

There is an old saying from the Bible that "iron sharpens iron", but when materials are of similar hardness, the sharpening process is slow. Thus, while silica based hones can be used to sharpen steel razors of similar hardness, the honing/sharpening process is slow. Thus, they tend to be better for the final polishing/finishing of an already sharp edge.

Hones based on materials that are significantly harder than steel will sharpen more quickly. Those include garnet as found in coticules, corundum (rubies and sapphires), and diamond. There are also man-made abrasives such as fused alumina ceramics, fused zirconia, silicon carbide, boron carbide, and boron nitride. Although diamond is found naturally, man-made diamonds are commonly used for abrasives.

One very popular finishing hone is the Thuringen. Escher stones are a vintage brand of thuringen stones. The stone is comprised of silica embedded in chalk. Since chalk is one of the softest minerals, it abrades quickly releasing quartz crystals that are responsible for the sharpening/polishing.

Since Arkansas stones are nearly pure silica, the crystals are not released so the action is more for polishing/burnishing rather than sharpening. This is especially true for the hardest Arkansas stones: translucent and hard black.

I have a friend who used to love honing on Arkansas stones. He found honing relaxing, so he would hone for long periods of time while watching TV. He has now switched over to the use of Shapton ceramic on tempered glass hones as they provide better feedback and are far quicker than Arks.