Crushing | PSP EngineeringKDC secondary cone crushers. KDC secondary hydraulic cone crushers are used for the crushing of hard, abrasive, non-sticky materials of compression strength up to 400 MPa (e.g. quartz, granite or basalt). Each crusher size is supplied with ungrouted crushing elements. The shape of… More info.hard kaolin crucher,Kaolin | New Georgia EncyclopediaJun 8, 2017 . Deposits are of three types: (1) "soft" kaolin, which breaks easily and is soapy in texture; (2) "hard" kaolin, which is more finely grained, difficult to break, and jagged in texture; and (3) "flint" kaolin, which has no commercial value because its high opaline silica content makes it extremely hard. Kaolin mining.