At that time, Mom and Dad in the yard Common crushed "cinder child", "cinder child" is to use coal ash and the soil and into the inside bend, and the general soil not, non-stick.
那时候，常见爸妈在院子里砸“煤渣子”，“煤渣子”是用煤灰和河湾里的泥土和成的，一般的土不行，不粘。
2
After picking with coal pick, 85% of the coal wil be crushed to 50mm size.