A number of minerals not before noticed as occurring in Britain have been described, and corroborative analyses thereof have been given, in the papers which I have, from time to time, published in the Transactions of the Royal Society of Edinburgh, and also, though to a smaller extent, in the Mineralogical Magazine.

Those which I now bring forward, have been analysed for the most part for a considerable time; but, as it must of necessity be long before I come to notice them, in their proper place, in my “Geognosy of Scotland,” it is well to announce their occurrence without further delay.

It is but seldom, at least in the experience of the writer, that a new mineral locality is now found in this country. By a mineral locality I mean, not a spot where one or two specimens may be gathered, but one at which there is a supply sufficient to entitle it to be recorded as a spot likely to be productive to a sequence of gleaners; and such as holds out hopes of its yielding specimens of more than average excellence.

It is well known to mineralogists, that Giesecke, who in the years 1806—13 travelled in Greenland, brought home from Julianehaab district some new minerals, which he handed over to the Copenhagen Museums. In 1853-4 Dr. Rink supplied the museum of the Copenhagen University with a large collection of the same minerals, mostly in large and fine specimens, and the same collections hove lately received a most valuable and considerable addition, through the travels of Mr. K. J. V. Steanstrup of the Danish Geological Survey of Greenland. Some of these interesting mino.rals, occurring in the Syenite on both sides of the fjords Tunugdliarfik and Kangerdluarsuk, have already long been known, whereas others had elther been not found there before or at least not analysed or described.

Having, since file date when the few observations chronicled in a previous number were made, ascertained some more definite facts with regard to these marbles, I now note these.

The localities in which I had previously observed the marble were all (through faulting and intrusions) so obscure as regards its relationships, that any conclusion as to its horizon was not warranted.

The Minerals Associates of Cassiterite.--These are much the same in Cornwall as have been observed in other tin-producing districts, as in Saxony, Bohemia, Brittany, Finland, Spain, the Malay Peninsula, Banca, Blitong, Queensland, New South Wales, Tasmania, &c. In the following lists of minerals which are associated with Cassiterite in the different kinds of country-rock in Cornwall, I only refer (a) to those which appear to have been formed contemporaneously with the Cassiterite, and (b) to those which have been observed in immediate contact with it and mostly deposited upon it.

The following substances have, for the most part, passed under the names here assigned to them; but they are themselves either ill-determined, or doubtful species: in some cases the name has been attached to certainly more than one specifically-distinct substance.

From Quiraing in Skye. It occurs in layers of an inch or two in thickness, among the amygdaloids. It is usually of a deep-red colour and has a greasy lustre, but is sometimes earthy and dull.

It falls to pieces in water, and may, by this property, and its uniformly dense structure, be distinguished from the red massive mesolite which sometimes occurs along with it.

A dark-grey, almost black, copper bearing mineral, somewhat resembling Redruthite in general appearance, but of a duller lustre and considerably harder; the hardness being between 5 and 6. In parts a bronze tint and lustre is apparent. The specimen exhibits neither crystals nor crystalline structure, it breaks with a well marked couchoidal fracture. Lustre somewhat resinous; streak shining.

Heated in a glass tube it gives off water, having a strongly marked acid reaction, from the sulphurous acid which is evolved. Before the blowpipe it does not fuse, colours the flame green, and acquires a dull black colour. Treated with strong boiling nitric acid it is rapidly acted upon, a bronze coloured residue being left, the residue when examined under the microscope presents a honey-combed appearance; the walls of the irregular cellular cavities are pale-brown and translucent and apparently composed of quartz; when the powdered mineral is boiled with nitric acid, a white residue of silica is left.

While agreeing with those writers who affirm that many of the members of this series are of the nature of schists, —sometimes almost flaggy schists, still, even when examined throughout their multitudinous varieties, it has to be affirmed that they are all gneissic schists; and, however fissile some of. these members may be, this is far from a sumcient reason for attempting to dispense with a time-honoured appellation;—one moreover which is more fittingly applied to them, than to the somewhat more generally hornblendic rock to which alone it has been proposed to confine its use.

The variety of saponite described in the following note was first obtained by Mr. Waiter Burns, of the Geological Society of Glasgow, from a quarry in the Cathkin Hills, about three miles S.S.E. of Glasgow, The quarry is hewn out of dark-coloured dolerite, rich in olivine, which restg on beds of felspathic ash. The dolerite has in places been converted into a green-coloured fibrous variety of saponite (Boulingite), which is found in veins of from 2 to 8 inches in thickness. This variety has been analysed by Prof. Heddle, as well as by Mr. G. Wallace Young and Mr. G. B. Hannay.

This paper forms part of a communication recently made to the Geologists Association, with some additional matter relative to certain criticisms passed upon Mr. Dunn's hypothesis as to the origin of the diamonds.

It is taken for granted on this occasion that the leading geological facts are known, I will merely, therefore, draw attention to a generalised section of Kimberley Mine, where one side represents the wall or reef bounding the pipe itself, and is thus constituted:—

A complete description of this mineral was given in Poggendorf's Annalen, vol. 132 (1867), p. 372, by Prof. vom Rath, who ascribed it to the oblique system with the elements, a : b : c=·361639 : 1 : ·116825 ; β=87°40′18″.

This paper gives a full account of the appearance and properties of the Meneghinite from Scrravezza, and of its association with Quartz, Galena, Blends, Chalybite, Copper Pyrites, Iron Pyrites, Calcite, and Albite; the results of the analysis also accord fairly with the previous determinations of Bechi and Hofmann, which give for the formula Pb4 Sb2 S7 or 4Pb S + Sb2 S3.

The great pyrites masses of the Sierra Morena, of which those worked at Rio Tinto are by far the most extensive, may be briefly described as contact deposits, which differ from such as are ordinarily met with only in size; and from ordinary fissure veins only in the circumstance that the cavities in which the minerals occur are bounded by dissimilar rocks.

A Very few dykes of the "greenstone type " are to be seen in the lower gneiss.

There are some localities at which the gueiss seems itself to have furnished the material of the dyke, if not to pass into it by insensible gradation.

One is a dyke seen in the vicinity of Badnaternag, on the north shore of Loch Assynt. Here the dyke runs along the strike of the rock.

It is a common chemical fact, that when a solution containing an alkaline silicate is acted upon by any reagent capable of separating the silica from the base, the silica is in the majority of cases thrown down in a solid form. The fact of this reaction is all that, as a rule, the chemist would look at: but in addition to the mere chemical fact of the precipitation of the silica, another most important element from the mineralogist's point of view is that of the form in which this precipitate of solid matter appears. This form naturally varies with the various conditions of the experiment, and it is by the study of these varying forms that the authors have sought to elucidate, experimentally , the wondrous and beautiful varieties of structure which are so familiar to us in the endless forms of silica occurring in nature.