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De Natura Fossilum
Textbook of Mineralogy
By GEORGIUS AGRICOLA, Mark Chance Bandy, Jean A. Bandy
Dover Publications, Inc.Copyright © 2004 Dover Publications, Inc.
All rights reserved.
Mineral substances vary greatly in color, transparency, luster, brilliance, odor, taste, and other properties which are shown by their strength and weakness, shape, and form. They do not have the variety of origins that we find not only in living matter but also in original matter. Moreover they have not been classified like the latter on the basis of the place where they pass their life since mineral substances lack life and with rare exceptions are found only within the earth. They do not have the differences in characters and actions which nature has given to living things alone. Great differences are not the essential features of minerals as they are of living and original matter.
Minerals have no dissimilar portions made up of similar materials. For example, a mineral we call "complex" nature forms from different kinds of simple substances, none of them dissimilar. The substances we call similar the Greeks usually call [TEXT NOT REPRODUCIBLE IN ASCII] while dissimilar substances are called [TEXT NOT REPRODUCIBLE IN ASCII]. Many minerals form from a single species, a few from many similar species. For example, each unit of red ocher is red ocher; each unit of alum, alum; asbestos, asbestos; gold, gold. All species of earth, congealed juice, stone, and metal are composed of single species except certain stones which are composed of two or more species. These stones are recognized by the presence of spots, veins, and areas that glitter like the stars. They may imitate different things by color variations. Thus from the minerals that come to our notice we learn these differences and are able to study their nature.
Color, taste, odor, and qualities of minerals which can be perceived by touch are most widely known because they are more easily recognized by the physical senses than qualities such as strength or weakness. A great many of these qualities are not known to everyone although those qualities which are learned through experience are widely known. For example, everyone knows that fire can be produced by striking flint with iron. On the other hand miners not only know this but also that fire will melt some varieties of flint, shatter others. Many people know that lodestone will pick up iron but only a few know that this power is weakened and destroyed if the stone is immersed in an acid.
In order to show the differences in minerals I shall begin by classifying them according to color, then I shall describe the nature of each form. Minerals vary greatly in color. Chalk, alum, asbestos, and Arabian marble are usually white. Persian marble, quartz, silver, quick silver, and tin are almost always white. Pnigitis, sory, smoky quartz, and Lucullian marble are black. Melia earth and one of the Eretria earths are ash-gray. Lapis lazuli and sapphire are blue. Chrysocolla and smaragdus are always green while some chalk and atramentum sutorium may be green. Ocher and gold are yellow. A certain variety of earth (rubrica) is red whence comes its name. Sard and carbunculus are red. Realgar has a ruddy color while amethyst is purple.
There are marked differences in shades of color in all of these minerals. For example, among the green minerals smaragdus is an intense green, chalk, pale green and chrysocolla an intermediate shade. Certain minerals have their own distinctive colors such as lead which is neither black nor blue-black and pure copper, between ruddy and red. Some minerals imitate the colors of other minerals and metals. Orpiment and yellow muscovite imitate the color of gold; one variety of aspilates, silver; chalcitis, copper; one variety of balanites, Corinthian copper; galena, lead; dactylus idaeus and basaltes, iron. Several minerals imitate the color of living things. For example, the gem icterias is similar in color to saffron; hematite, to blood; prasius, to the leek; aspilates, to fire.
Many minerals have two mixed or separate colors. Taking up those with mixed colors first, some are bluish white such as jaspis which is also called borea. Some are greenish blue such as armenium, some whitish red, as aphrodisiace. Some minerals are in part yellowish white as xanthos; in part blackish red such as the three varieties of batrachites. Certain black minerals have a purplish tinge, for example alabandicus lapis.
Regarding minerals with two separate colors, those having white and black bands have been used more than all others in our times since they are so admirably suited for carving. These stones occur in nature with alternating white and black bands. Apsyctos has a black groundmass cut by red veins while nasamonites has a red groundmass cut by black veins. Leek-green heliotropios is cut by blood-red veins. Lapis lazuli contains sparkling golden points of light.
Some minerals have three separate colors. Stones found in glass sands are white, red and yellow; white, gray and black; even white, green and blue. The white groundmass of the mineral "Egyptian agate" is cut by black and sard-red veins according to Jacchus. Eupetalos and orca have four different colors, eupetalos, blue, flame-red, vermillion and green; orca, black, dark yellow, green and white. Hexacontalithos and panchros have even a greater number of distinct colors and the names of these stones come from the variety of colors they show. If different color combinations are found in stones such as these latter ones they do not form new varieties but if such variations occur in other minerals they usually do. Finally, several minerals such as the mineral paederos show a play of colors similar to that seen on the neck feathers of certain African fowl when ruffled in anger and on the feathers of the peacock or pigeon when spread in the sun. These minerals also show a play of colors when inclined in different directions.
Although certain minerals are transparent most minerals are not. None of the earths, metals, or rocks is transparent. Out of the large number of mixed minerals proustite is the only transparent one, a deep red, and even this one is not always so. Of all the marbles only some parts of a few pieces of phengites marble are transparent and among the stones, properly named, only selenite, magnetis formed in thin crusts, and gypsum, the last two minerals only very rarely. Four congealed juices are transparent, halite, nitrum, alum, and atramentum sutorium. Many gems are transparent and amber commonly so. Some of the transparent gems change color when inclined, for example, eristalis (opal), which changes from white to red. Others may become clearer when inclined as does the Carthaginian smaragdus. Gems which can be scratched with steel, especially those which are spherical and protrude like the eye appear to be white when held in the sunlight and have the same color as the rest of the mineral, although somewhat lighter, when held in the shadow. But of these some are brilliant, others dull; some are lighter, others dark. These differences can be observed in the carbunculus.
Luster, brilliant luster, is found in all genera of minerals and I shall mention only a few. Among the earths creta argentaria has a brilliant luster and the same is true of all transparent congealed juices, all transparent stones, all gems, and the native metals. Luster occurs throughout the entire body of the most valuable gems, magnetis, and the mineral we call armatura. On the other hand some minerals do not have a luster throughout all the body. Certain micas have a luster only within the body of the mineral and similarly misy has a golden luster, creta argentaria, silver. Also there are stones to which they attach very thin foils of pure gold, silver, copper, and other metals in order to increase their luster. Among the lustrous minerals some reflect an image, for example, smaragdus, the carbunculus found at Orchomenus, Arcadia, cepites, cepionides, and hephaestites. All hard stones will reflect an image when polished. Obsidianus lapis that is called jet reflects an image which resembles a shadow. Although all minerals have this property, the luster we usually see is more often due to art than to nature. The luster of marbles, gems, and metals is the result of polishing. A luster can be given to glutinous earths by merely rubbing them with the finger nail.
I now take up taste. Some minerals have a sweet taste, for example, melitites and galactites; Samia earth and marl, an oily taste; nitrum, a bitter taste; halite, a salty taste; lime and spodos which is found in mines, an acrid taste; red ocher, an astringent taste; and certain earths which have absorbed an acidulous juice, an acidulous taste. Some minerals have a mixed or confused taste, for example, atramentum sutorium and related species which have both an astringent and acrid taste. One perceives the taste of congealed juices by placing them on the tongue, especially salt, alum, soda, iron sulphates, and related species. Earths which have absorbed these juices, as well as stones, are tested in the same way. Astringent earths adhere to the tongue. Some earths, if not all, when placed in a vessel, covered with sweet water, and then worked with the hands, give their taste to the water. The water will be found to have the same taste as the earth. A kind of juice is given off by certain stones such as hematite and schistos when they are ground in a mortar. Gems and the stones which melt in a fire do not give this kind of juice. Each metal has a distinctive taste which can be ascertained by placing water in a vessel made from the metal and allowing it to stand for a long time. The metal then gives its taste to the water. The taste of copper is very bitter and unpleasant, that of iron less so while the taste of tin is the weakest of all metals.
The odor which minerals give off according to their strength and nature will be considered next. That of sory is so foul it causes nausea. Certain minerals have an odor when struck with an iron or stone. Treated in this way the Hildesheim marble gives off an odor of burning horn. Recently a silver vein has been discovered in a prospect named St. Fabius and St. Sebastian near Marienburg and the ore from this vein, when broken in the mine or after it is carried outside, gives off an odor which is pleasing to everyone. Prince Henry, who was present at the time the vein was discovered, was so pleased that he exclaimed, "This is Calcutta, India." Aromatic gums come to us from that city. An odor is also obtained from some minerals by crushing them in a mortar. Realgar, treated in this way, gives off an odor of sulphur. Certain minerals give off an odor when burnt in a fire, for example, realgar has an odor of sulphur; amber, for the most part, of myrrh; jet, of bitumen. Camphor has an acrid odor and the fire which heats it increases its pungency as it is carried upward to the cover of the vessel. Stones and earths which do not contain bitumen give off almost no odor when thrown on a fire. When heated gold has a sweet odor which is detected with difficulty; silver a somewhat fetid odor; copper and iron a fetid odor; lead, bismuth, and zinc a dull odor. Many mixed minerals smell of bitumen, many of sulphur. Some cadmia fossilis has an odor of garlic. The geodes from Misena, the stone from Berninger and fragments of a rock from Aldenberg have an odor of violets which comes, not from the stone, but from the adhering moss.
Minerals have warmth and coolness, moisture and dryness. To anyone who touches minerals lightly almost all appear to be cold but there are many which warm the body if they are held against it for a long time. Some minerals are warm, having been heated by the fires which rage within the earth. This genus is commonly found in fiery localities. Sometimes a mild subterranean heat warms them, for example, the vein recently found in the Joachimsthal valley and named the "Stella" and the vein found some years ago at Annaberg and named the "Obliqua." But this mild heat found in minerals is not excessive for the miners working in pits and mines usually do not notice it. But when ore is first brought out to the air, if it is in the form of small pieces so that the hands can be buried in it, the ore not only heats them but burns them painfully for a short time. Any very hard stones which are naturally cool become warm when rubbed or pounded together. The same is true of metals.
Although minerals are naturally dry, often projecting parts can be completely saturated with water. All earths can be saturated with water and certain congealed juices.
Minerals differ even more in other qualities which are perceived by touch and which reveal the position of some, and in the well-known qualities due to strength and weakness, namely, unctuousness and meagerness, density and porosity, hardness and softness, roughness and smoothness, heaviness and lightness, and many others.
Some minerals are unctuous such as marl, sulphur and jet, while others, such as ocher, salt, sandstone, and almost all stones, are meager. There are many more meager minerals than unctuous but among the latter there are some which are completely unctuous such as sulphur, bitumen, amber, jet, etc., and some which are semi-unctuous such as spinus and many others which I shall classify as "mixed." Although most minerals are dense, some are porous, for example, pumice, travertine, and the chalk used by painters. The parts have not been joined and connected, one with the other, on all sides and they contain much air. Many minerals are hard but stones and metals are especially so. Spodos, lime, and earths which have been moistened with water are soft. Emery, Melia earth, and the earth they call "tripela" (tripolite) are rough for these have sharp points. Most gems, refined metals, and even native metals, the parts of which are uniform, are smooth. Generally all minerals are heavy although jet, mineral ebenum, pumice, and travertine are light. Some minerals have openings too small to be seen by the eye and in these is a quantity of air which mixed with earth and water is contained in the entire body of the mineral. A mineral which is full of openings that can be seen by the eye is called [TEXT NOT REPRODUCIBLE IN ASCII] in Greek and fistulosa in Latin.
Minerals differ in the degree of the qualities mentioned above, for example, amber is more unctuous than jet, sandstone is more meager than ocher, and another is intermediate between unctuous and meager. The concept of degree in qualities was understood by the older writers on agricultural subjects for they say that one earth is rich, another poor, another intermediate.
Now I shall consider how minerals differ in other well known qualities due to strength or weakness, namely how they resist destruction. Certain minerals dissolve in moisture, such as earths, halite, nitrum, alum, atramentum sutorium, etc.; others in fire, such as the stones the Greeks call [TEXT NOT REPRODUCIBLE IN ASCII] and our miners, if I may be allowed to translate the German word, call fluores. Many of these are very similar to gems. Transparent gems themselves melt in fire as well as silex, stones which produce the sands from which glass is made, metals, and especially many mixed minerals. Some of these melt quickly, some slowly. Earth which if soft, porous, and meager dissolves quickly in liquid while earth which is hard, dense, 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 [TEXT NOT REPRODUCIBLE IN ASCII] 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 [TEXT NOT REPRODUCIBLE IN ASCII] 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.
Excerpted from De Natura Fossilum by GEORGIUS AGRICOLA, Mark Chance Bandy, Jean A. Bandy. Copyright © 2004 Dover Publications, Inc.. Excerpted by permission of Dover Publications, Inc..
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Table of Contents
|Latin Mineral Index||225|
|Greek Mineral Index||233|