These are acrylic colors produced by Matsuda Oil Colour Co., Ltd. They have high pigment concentration, creating rather calm textures without having excessive glossiness specific to the usual acrylic colors.
Mineral pigments are mainly used in Japanese paintings and made from azurite, malachite, or coral. They are powder pigments and do not adhere, and so vehicles such as animal glue can be mixed for adhesion. The fineness of the powder is classified by number and generally indicated from No. 5 to No. 13 and white. The smaller the number, the finer the particles, white being the finest, and the lighter the tone.