Ultramarine blue from Asturian “hard” kaolins

Ultramarine blue made with Asturian refined hard kaolin from deposits associated with Armorican quartzite, is compared with the pigment made with China kaolin, both produced in the same synthesis conditions. Properties after a deep characterization (XRD, IRFT and Ramman Spectroscopies, Light Reflectivity, Colorimetry and Micro-analysis) showed that the Asturian Teresa mine kaolin is good enough, once washed and classified, to produce a good blue pigment. The pigment is quite comparable in quality to the one produced with China kaolin. Moreover, it can be obtained from a cheap and abundant material which so far had only been used for calcined fire-clay raw materials, used in low alumina refractories and castables production.