Slips.

stance also remarked by Dolomieu, who says that such granites differ from those of the mountains, as the grains are larger, the substances less interwoven and coherent, while each has a greater tendency to regular crystallisation. But, on the other hand, Charpentier observed, in various parts of Saxony, veins of granite in mountains of gneiss; the granite consisting of white quartz in very small grains, mica in fine particles, while the felspar was scarcely distinguishable from the quartz*.

The slips or dykes found in coal mines, may also be classed among the veins of stone. They chiefly consist, as already mentioned, of basaltin and basalton, clay-rock, and argillaceous sand

stone.

But the denomination of veinstones has been more strictly confined to the substances found in metallic veins, which, from their confined nature, perhaps more properly belong to lithology; whence only a few observations are here offered, by way of supplement to a treatise on rocks; as they often perplex the learner, and sometimes even the adept, by combinations which do not occur in mountain masses. A short account of these veinstones, given by an honest practical miner, may Account by not be unacceptable. "What I call veinstone,

Williams.

* Ib. No. 16, p. 22.

is a compound mineral concretion of various colours, appearances, and degrees of hardness, and not unfrequently of various colours in the same mass, though white often prevails. This compounded stony concretion is called by miners a rider, perhaps from its riding the vein, or separating it longitudinally into two or more divisions. This mineral stone is hard and heavy, sometimes compact and solid, but frequently cracked and cavernous, rising in irregular and mishapen masses, and generally exceeding hard. A rider frequently contains a variety of different substances or species, as well as different colours, in the same mass, such as spar, quartz, fragments of the rocks near the vein, sometimes pyrites, and often ore in grains and flowers, and sometimes different ores, as lead, copper, &c. in the same mass, and all these strongly coagulated or concreted together by a whitish or a brownish-white substance, resembling quartz and agate, which seems to have enveloped the several articles in the composition when the whole was in a fluid state. I call this veinstone, as I think the term should be the most intelligible to naturalists, it being always found in veins, upon the superficies of them, and in fragments and masses lying about upon the face of the ground, which have slidden, or been forced off, the superficies of veins. But the veinstone does not always contain so great

a variety in its composition. It is often pretty white, and appears like a quartzy concretion of a porous, or rather a cavernous texture; and the inside of the caverns, though small, frequently con tains a brownish ferruginous soft soil of a snuffy appearance; and sometimes the insides of these small caverns are finely lined with great numbers of pointed or prismatical crystals, generally exceeding beautiful, and sparkling like diamonds. But all the veinstones, or riders, are not white nor whitish. In many places they are of a brown, or a reddish-brown, and several other colours; but the whitish colour most commonly prevails. Strong wide veins often contain a large rib of this veinstone betwixt the sides, several feet thick; but in all degrees of thickness, from a few inches up to several feet, I have seen strong bold veins carry such a rib or body of this stone as to appear in a ridge above the surface of the ground a great way, the superficies of the native rock being withered, and wasted away from both sides of it."*

This description clearly applies to quartz: and he afterwards proceeds to mention that the chief spars, found in mineral veins, are the calcareous and cauk-spar, since called barytes. The soft mineral soils found in veins, are a white, or whitish

• Williams, Min. King. i. 284.

bole; a red unctuous ferruginous clay; with other kinds and colours, especially that called gur by the Germans, of various tints of brown, and resembling rappee, and sometimes Spanish snuff. The peach of the Cornish miners, chlorite, or green bole, is also frequent.

From the account which Williams gives of the rider, in the very imperfect mineralogical language of that period, it would appear that he means to indicate a vein of ferruginous quartz, generally found to accompany metallic ores. By his description it is very rough and irregular, and full of little cavities, containing a ferruginous powder like snuff. The whitest parts have some resemblance to what is called a bur-stone, chiefly used for mill-stones, their irregular surface serving the purpose of trituration: but the rider generally contains heterogenous substances, as ores, pyrites, spar, fluor, &c.* It seems often to approach keralite, or the hornstein of the Germans, which sometimes even forms mountains, replete with silver and other ores.

It would seem that the cavities containing druses of small crystals, chiefly occur in the purer portions of the rock; and his account of this beautiful kind of veinstones merits transcription.

• Will. i. 379.

Gur.

Rider,

Lochs.

"Most of the mineral spars are frequently found shot into prismatical, cubic hexagonals, or other figures. These figured crystals are generally transparent, and very beautiful. It is a great curiosity to behold the inside of some of the large cavities in which they are formed. These open caverns are frequently met with in hard mineral veins, and they are generally called by miners lochs, or loch holes.

"The miners know nothing of these cavernous vacuities until they strike into them, as they advance in working; and they are of various dimensions, from the bigness of a nut, up to room enough for three or four men to turn themselves in them.

"The magnitude of these caverns is generally in some proportion to the capacity of the veins in which they are found; and the insides of them frequently exhibit all the variety, beauty, and splendour of the most curious grotto-work.

"There is commonly a hard concreted stony crust, called druse, adhering to the inside, of the cavity; out of which, as out of a root, an innumerable multitude of short prismatical crystals are shot, which sparkle like a thousand diamonds with the candle, or when brought up to the sun. Between these clusters of mock diamonds, and sticking to them promiscuously, there are often