Obsidian

An ore that is considered a type of volcanic rock.

It is black in appearance, has properties similar to glass, and has the same hardness as glass.

When broken, it shows a very sharp fracture surface, and because of its sharpness, it was once used for stone tools such as knives and arrowheads for bows and arrows.

Particularly in the Aztec civilization of Mexico, it was used for macana (maquahuitl) blades and knives used in sacrifices, and the creation of an empire was largely due to the existence of veins from which this ore could be extracted in abundance.

Even today, there are situations where sharpness is required, and it is sometimes used in surgical scalpels.

黒曜石