The minerals described in this paper were obtained by Mr. Arthur L. Collins last summer, and their mode of occurrence is explained in the accompanying note by him. My description will deal in detail with their crystallographic characters.

It has long been known that several of the felspar-porphyry dykes (Elvans) of the West of Cornwall contain crystals of pinite--apparently pseudomorphous after iolite--as an accessory mineral, and similar crystals occur.in the granite in several places.

In the parish of Breage there are several of these dykes running towards the sea in a south-easterly direction, which are somewhat largely used as road-material. That which reaches the sea at Praa is in places thickly charged with the pinite crystals, and the same in a somewhat less degree may be said of the dyke which passes from the village of Trew through Great Wheal Fortune.

The specimen which is the subject of the present note consists of a group of large rude, reddish crystals of tetrahedral aspect, which in colour, lustre, and general appearance, resemble garnet; they were formerly supposed to be garnet pseudomorphous after some tetrahedral mineral, and the original mineral was presumed to have been fablerz, on account of the size of the crystals, which measure as much as 3 to 5 centimetres across.

In the early part of 1890 I noticed in some of the workings of the Torreon Mines, and chiefly on a decomposed ehalcopyrite or in close connection therewith, a greenish-blue to sky-blue lamellar coating about inch in thickness, with sometimes isolated plumose groups of scaly crystals having a pearly lustre. Both appearance and mode of occurrence of the mineral led me to think it a basic sulphate of Copper, probably cyanotriehite, or possibly a new species. Soon afterwards however, it was noticed that when the ore, as sorted for smelting, contained any quantity of the pale blue incrustation the cyanide assay failed to give accurate results in the estimation of copper, and on testing such ore qualitatively for zinc quite an appreciable quantity was found. Want of leisure prevented a more extended examination, but a good many specimens were selected and carefully preserved.

On examining a specimen of manganite from Harzgerode, consisting of iron-black crystals of apparently long-prismatic habit, it was found that they were, in most instances, composed of many individual crystals, the latter ranging from about two to four millimetres in length. As they seem to differ in habit, so far as I know, from the crystals of manganite hitherto described and figured, a short account of them, pending more careful investigation and measurement, may be of interest.

Few, if any, analyses of British aragonites have been published; that which I now submit was executed upon a specimen forwarded to me by Professor Heddle, who has supplied me with the following notes of its occurrence.

It was obtained by him at Sobul Hill, in Unst, Shetland.

The west side of the hill of Sobul is pitted for the extent of nearly a mile with quarry holes, opened in a search for chromite.

The crystalline form of orpiment was first determined by Mohs (Grundriss der Mineralogie (1824), 2, 613).

His measurements, which he is careful to state were only approximate, gave an angle of 79°20' for the prism, and 83°7' for the brachydome; the plane of perfect cleavage being taken as the macropinakoid, and the crystals being referred to the orthorhombic system.