William Phillips

“ It is remarkable enough that tin, which, in the metallic state, is one of the lightest metals, surpasses in specific gravity, when in the state of oxyd, the greater part of other substances of the same class, whether simple oxyds or composed of an oxyd with a mineralizing substance. The weight of oxydated tin is such, that its difference with that of metallic tin is but about one twentieth at least ”

“ With Blende on quartz, from St. Agness.
In Mispickel—with mispickel on schist.
In Wolfram—with wolfram and dark brown gossan—with woltram and chlorite from Pednandrae mine—with the primitive crystal of wolfram, mispickel and yellow copper ore, from Huel Fanny. The science of mineralogy is so intimately connected with some branches of the mathematics, that he who pretends to the former, unassisted by a knowledge of the latter, may perhaps be considered as pursuing it rather as an amusement, than as an object of scientific research. I confess myself to be exactly so circumstanced. ”

“ The incidences subjoined, are, for the most part, the result of many perfect agreements of each, on different crystals. In no instance has an average result been noticed. All are not to be relied on with equal confidence. The plane forming the 9th modification of the primitive octahedron is always so striated, and those of the 3d and 10th, are always so dull, that the incidences of those planes with any other in the subsequent series can only be considered as approximations. ”

“ Not only are the same crystalline forms generally apparent on each cabinet specimen, but even entire veins seem to be productive principally of the same varieties. In the tin-stone of Polgooth near St. Austle, I have rarely seen any other than minute crystals of the form of fig. 66, Pl. 18. That produced by Pednandrae, an extensive tin mine close by the town of Redruth, is almost uniformly of the macle described by fig. 208. Pl. 25. From Huel Fanny mine, which produced tin only in the shallow part of the copper vein, I have never observed any other forms than those described by figs. ”

“ The seeming confusion produced by the macle, [17] is very often much augmented by circumstances apparently resulting from no law, by which parts of crystals are jumbled together, so as to form a whole, that can only be understood by a long and patient investigation, which in the end serves only to satisfy the observer of the absence of all regularity in the disposition of the several constituent parts, although each may be separately defined. ”

“ For whatever has been said tending to shew a connexion between the fractures that have been described, and a crystal delineated by fig. 15. relates, with equal aptitude, to one having either a longer. or a shorter prism, and equally well to one having no prism at all: for it will be seen by fig. 17. that the form of fig. 15. is merely the result of a decrement on the edges of an octohedron formed by the meeting of its two pyramids base to base; which octohedron is given by itself fig. 18. as the primitive form of the oxyd of tin. ”

“ Thus is the conjecture of Haüy before cited, that he perceived the natural joints parallel with the planes of the prisms verified. I have also obtained numerous cleavages parallel with the diagonal of the prism, but have in vain attempted it in a direction perpendicular to its planes. ”

“ Others give only a light green when placed on a coal, without dying, but fly when placed in the tire.
↑ The reflecting goniometer is so delicate an instrument, that great care is requisite in the choice of the crystals subjected to it for the admeasurement of their angles. It often happens that those of apparently the most beautiful surfaces are unfit for this purpose; the most clear reflections alone can be relied on, and even then only by comparing the results of trials on many crystals. Some of the first attempts gave an incidence of 2 on 2 over the apex of the fig. ”

“ Colour—whitish, either translucent or opake; it is sometimes of a resin yellow, but more often of a deep brown somewhat reddish, more frequently blackish, or black; occasionally brick-red, but in that case generally bears in some respect marks of having been exposed to the action of fire. ”

“ It seems to have formed the principal part of a vein, being accompanied on each side by decomposing fluor, which has an ochreous crust similar to the gossan of the mines. On being placed on a live coal it gives a green light, nearly as splendid as the chlorophane, and does not fly ”

“ Each of the eight solid angles of this figure, therefore, is composed of two portions of the common prism, fig. 196; giving, by the common goniometer, along the edges a b c, an angle somewhat more than 112°, which, generally speaking, is the same as that l m f; fig. 200; the plane 1 on 1, over the edge between them, which is that of the common prism, also gives an incidence of 90° corresponding with that of the planes 1 on 1, fig. ”

“ Pl. 20. By fig. 107. the planes are shewn in an advanced state.
The two figures which alone compose the series of this exhibit its planes very differently, and on all the crystals represented by these two figures, they are so uneven, or irregularly striated, as to render it wholly impossible to subject them to the reflecting goniometer. This modification is extremely rare. The crystals described by fig. 108. have I believe been brought only from the mine called Huel Fanny, west of Redruth. ”