This substance forms handsome black crystals of very high lustre, which, when small and scaly, constitute micaceous iron ore. Both, when rubbed down, furnish a dark red powder of no particular beauty. Micaceous iron ore forms the transition stage into frothy hematite, or iron cream, the sole difference being that the crystals of the latter are much smaller, and the scales finer, the iron-black colour passing gradually into cherry red. At the same time, the lustre, though still high, loses most of the metallic sheen exhibited by micaceous iron ore. HEMATITE The variety known as hematite or bloodstone, sometimes occurring as shiny nodules, is distinguished by its handsome red colour. Some of the lumps are composed of long, thin crystals grouped about a common centre so as to form a globular mass. Despite its bright colour, the hardness of hematite (between 3 and 5) prevents it from being used as a pigment, the value of the product not being commensurate with the cost of reduction. RADDLE There are numerous deposits of red ironstone, in the state of fine earth, where the operations of grinding and levigation have, to a considerable degree, already been carried out by Nature. These deposits form the mineral which, under the name of raddle, is often used as a pigment for ordinary paints. It may be considered to have originated in the transformation of red ironstone, by the natural forces that can everywhere be seen disintegrating rocks, namely water and frost, into a fine powder, which has been transported, often over long distances, by water, and has finally settled down. In places where the process has been carried out in this manner, the raddle will be in a condition, as regards fineness of division and beauty of colour, that leaves nothing to be desired, and the material itself is ready for use as a very valuable pigment. Large deposits of this kind, however, are of rare occurrence; but there are plenty in which the ferric oxide is associated with varying quantities of clay, sand, and sometimes lime. The conditions here are on all fours with those of clay, which, too, has been formed in a similar way. Pure clay, the so-called kaolin, is a highly valuable material, whereas ordinary loam--highly contaminated clay--is only of low value. In judging the quality of raddle as a pigment, the presence of impurities is of less account than their nature; and in some cases a very highly contaminated raddle may be worth far more, as a pigment, than one containing only very small admixtures of extraneous substances.