Pine Flower Stone Seal 6cm x 6cm Pine Flower Stone is produced from Stone Mountain on the banks of the Hunto River at the foot of Changbai Mountain in Jilin Province, China. The stone quality has fine texture, is hard, and has a moist feel, so it is also called Pine Flower Jade (Shoka-gyoku). It is described in the Qing Dynasty's official "Xiqing Yanpu" as "Pine Flower Stone comes from Stone Mountain on the Hunto River. It is green, has luster, moisture, and fine texture." Pine Flower Stone belongs to microcrystalline limestone and exists in the strata of the Sinian Period (600 to 800 million years ago). Its main mineral components are calcite and quartz, with small amounts of sericite and clay minerals. The stone quality is hard and tight, with a softness, fine texture, and a balance of strength and flexibility, with sharpness within the fineness. Its characteristics are that the sharpness of the ink doesn't wear down even after long use, the ink is not at all diminished, it leaves no ink residue when washed, and it is difficult to dry even when water is retained. Its hardness (Mohs hardness) is 4-5, and when tapped, it emits a clear metallic sound with a lingering echo.