Made Pigments Frits and Lakes

A variety of mineral ores, mosfly copper minerals such as malachite and chrysocolla, were probably fhe mosf used green pigments in the past. Various green minerals derived from mefals ofher than copper, such as green earth (see below) were used in confined regions. 

Green earth, best known by the Italian name terra verte, is probably the main green pigment not derived from copper. Terra verte is a mixture of two minerals, caledonite and glauconite, both complex silicates of aluminum, calcium, iron, magnesium, and potassium silicate (Grissom 1986). 

Cutting, grinding, and shaping stone, and in particular burnishing and polishing the surface of stone as well as metals, requires the use of abrasive materials that are harder than the solids to be cut, ground, burnished, or polished. Sapphire and ruby, two very hard gemstones, for example, can be cut or polished only with the assistance of diamond powder, an abrasive that is harder than sapphire or ruby. Diamond is the hardest material 

Crystalline solids have a regular geometric shape bound by plane surfaces that intersect at characteristic angles. Their shape results from the arrangement of the particles (atoms, ions, or molecules) within the crystals, in an 

The most characteristic and unique property of crystalline solids is however, neither the shape of their crystals nor the relative size of the crystal faces, but the angle between any pair of crystal facets. For any substance, the angle between the crystal facets is constant and invariable, regardless of the overall shape or size of the crystals. Under some circumstances a substance may form short, wide crystals, while under others, the 

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