《天工开物·中篇·燔石》
方圆百里之间，必定会有可供煅烧石灰的石头。这种石灰石以青色的为最好，黄白色的则差些。
百里内外，土中必生可燔石，石以青色为上，黄白次之。
Within a hundred miles, there will definitely be stones available for burning lime. This limestone is best when it is blue, and yellowish-white is worse.