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Book I Minerals color, taste, odor , physical properties of gemstones and minerals such as emeralds, diamonds, rubies, sapphires

Book I Minerals color, taste, odor , physical properties of gemstones and minerals such as emeralds, diamonds, rubies, sapphires Page of 251 Book I Minerals color, taste, odor , physical properties of gemstones and minerals such as emeralds, diamonds, rubies, sapphires Text size:minus plus Restore normal size   Mail page  Print this page
10
DE NATURA FOSSILIUM
and unctuous dissolves slowly as does halite, nitrum, alum, and atramentum sutorium. Artifical minerals dissolve quickly. The same is true of natural efflorescences of halite and nitrum. These minerals do not occur within the earth. Bismuth, tin, and lead melt quickly in a fire; the other metals with greater difficulty; iron with the greatest difficulty. Stones similar to gems melt more quickly than true gems. Minerals which dissolve in a liquid almost never melt in a fire but are either reduced to a powder or consumed, as I shall discuss a little later. On the other hand, minerals which melt in a fire are not soluble in liquid.
Some minerals such as earths, certain stones, and sulphur become soft in a liquid and iron and copper become soft in a fire. Those minerals which become soft in a fire and correctly called μαλακτά by the Greeks since they can be worked so that, with one blow of the hammer, the surface is spread out and at the same time lowered. However minerals which are softened by a liquid are not called μαλακτά for although they become soft they cannot be flattened or stretched like a sinew, membrane, or piece of leather without breaking. Some of the latter minerals become soft quickly, for example the earths, while others, such as hard stones, soften slowly. All minerals which are not softened in a fire can be softened by water. For example, a portion of the hardest marble buried within the earth may be softened by water while the rest retains its hardness.
Some minerals are damp such as earths and sulphur, while metals and transparent gems are not. Damp or moist minerals are those which be­come soft when sprinkled with water. Halite, nitrum, alum, and atramen-tum sutorium are not moist since they dissolve instead of softening when sprinkled with water. Since all minerals contain earth and water those which dissolve or soften in water consist mostly of earth and those that soften in fire contain an abundance of water. Some minerals are pliant and sticky such as soft bitumen. Some are so coherent that when drawn out it is difficult to separate them from the parent mass. Similarly, unctuous earth which has been softened with water is sticky and, as the poet affirms,
"It sticks to the fingers like pitch"2
Certain minerals, having been crushed, are broken down with ease in water. These are called ψαθυρά by the Greeks. Meager earths belong to this class and many varieties are found in mines. A few minerals are flexible, namely asbestos, the only mineral that is spun and woven, and metals that occur in arborescent shapes. If these wires of native metals are straight they can be bent in any direction, and if bent they can be straightened. Other minerals can be neither straightened nor bent.
Most minerals are friable, i.e., they can be pulverized by either pounding or grinding them in a mortar. A very few are cleavable, i.e., capable of being split into two parts such as talc which occurs as tabular aggregates.
* Virgil.
Book I Minerals color, taste, odor , physical properties of gemstones and minerals such as emeralds, diamonds, rubies, sapphires Page of 251 Book I Minerals color, taste, odor , physical properties of gemstones and minerals such as emeralds, diamonds, rubies, sapphires
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