The space between two veins is called an intervenium; this interval between the veins, if it is between venae dilatatae is entirely hidden underground. If, however, it lies between venae pro/undue then the top is plainly in sight, and the remainder is hidden.
Venae profundae differ greatly one from another in width, for some of them are one fathom wide, some are two cubits, others one cubit; others again are a foot wide, and some only half a foot; all of which our miners call wide veins. Others on the contrary, are only a palm wide, others three digits,
immediate causes are heat and cold; next in some way a stony juice. For we know that stones which water has dissolved, are solidified when dried by heat; and on the contrary, we know that stones which melt by fire, such as quartz, solidify by cold. For solidification and the conditions which are opposite thereto, namely, dissolving and liquefying, spring from causes which are the opposite to each other. Heat, driving the water (humorem) out of a substance, makes it hard; and cold, by withdrawing the air, solidifies the same stone firmly. But if a stony juice, either alone or mixed with water, finds its way into the pores either of plants or animals .... it creates stones. ... If stony juice is obtained in certain stony places and flows through the veins, for this reason certain springs, brooks, streams, and lakes, have the power of turning things to stone."
On the Origin of Metals, he says (De Ortu, p. 71): " Having now refuted the opinions of others, I must explain what it really is from which metals are produced. The best proof that there is water in their materials is the fact that they flow when melted, whereas they are again solidified by the cold of all’or water. This, however, must be understood in the sense that there is more water in them and less ’earth ’; for it is not simply water that is their substance but water mixed with ’ earth.’ And such a proportion of ’ earth ’ is in the mixture as may obscure the transparency of the water, but not remove the brilliance which is frequently in unpolished things. Again, the purer the mixture, the more precious the metal which is made from it, and the greater its resistance to fire. But what proportion of ’ earth ’ is in each liquid from which a metal is made no mortal can ever ascertain, or still less explain, but the one God has known it, Who has given certain sure and fixed laws to nature for mixing and blending things together. It is a juice (succus) then, from which metals are formed; and this juice is created by various operations. Of these operations the first is a flow of water which softens the ’earth’or carries the ’earth’along with it, thus there is a mixture of ’ earth ’ and water, then the power of heat works upon the mixtures so as to produce that kind of a juice. We have spoken of the substance of metals; we must now speak of their efficient cause. . . (P- 75): We d not deny the statement of Albertus Magnus that the mixture of ’earth’and water is baked by subterranean heat to a certain denseness, but it is our opinion that the juice so obtained is afterward solidified by cold so as to become a metal. . . . We grant, indeed, that heat is the efficient cause of a good mixture of elements, and also cooks this same mixture into a juice, but until this juice is solidified by cold it is not a metal." ... (p. 76): This view of Aristotle is the true one. For metals melt through the heat and somehow become softened; but those which have become softened through heat are again solidified by the influence of cold, and, on the contrary, those which become softened by moisture are solidified by heat.
On the Origin of Compounds, he states (De Ortu, p. 80): " There now remain for our consideration the compound minerals (mistae), that is to say, minerals which contain either solidified juice (succus concretus) and ’ stone,’ or else metal or metals and ’ stone,’ or else metal-coloured ’ earth,’ of which two or more have so grown together by the action of cold that one body has been created. By this sign they are distin- guished from mixed minerals (composita), for the latter have not one body. For example, pyrites, galena, and ruby silver are reckoned in the category of compound minerals, whereas we say that metallic ’ earths ’ or stony ’ earths ’ or ’ earths ’ mingled with juices, are mixed minerals; or similarly, stones in which metal or solidified juices adhere, or which contain ’ earth.’ But of both these classes I will treat more fully in my book De Natura Fossilium. I will now discuss their origin in a few words. A compound mineral is produced when either a juice from which some metal is obtained, or a humour and some other juice from which stone is obtained, are solidified by cold, or when two or more juices of different metals mixed with the juice from which stone is made, are condensed by the same cold, or when a metallic juice is mixed with ’earth ’ whose whole mass is stained with its colour, and in this way they form one body. To the first class belongs galena, composed of lead juice and of that material which forms the substance of opaque stone. Similarly, transparent ruby silver is made out of silver juice and the juice which forms the
