Mineralogy Of Scotland Research Articles

III. The County Geognosy and Mineralogy of Scotland

The chapters of this work purport to be chronicles of the present state of our knowledge of the mineralogy of the northern portion of the kingdom. The geognosy and lithology are treated of to such an extent only as, in the first place, to explain the position of the minerals ; and, in the second, to aid future investigators in their explorations.In these chapters, in order to do full justice to the work of others, the authority for, and the original discoverer of every locality mentioned, will be quoted, wherever known.The author, having attempted to visit every known mineral locality to the north of the Forth and Clyde, and having succeeded in this attempt with less than half-a-dozen exceptions, is able in most cases to authenticate, or the opposite, as the case may be, the statements of previous observers.

1. Chapters on the Mineralogy of Scotland. Chapter I.—On the Rhombohedral Carbonates

Professor Heddle read a paper on the “Rhombohedral Carbonates occurring in Scotland,” the first of a series of Chapters intended to embrace the analytical results of an investigation of all unknown or insufficiently determined Scottish species.In this paper many analyses of the carbonates were submitted; and the pseudomorphic changes taking place in these were referred to in a special manner.

XIV. —Chapters on the Mineralogy of Scotland. Chapter Third.—The Garnets

Abundant as are the localities in which garnet is found in Scotland, there are but few which yield specimens such as can be analysed.This is on account of an intermixture of quartz—for the most part in a granular form—the granules being promiscuously scattered throughout the mass of the crystals. In three localities the intermixture is not promiscuous, but has been governed by some intermittent crystalline action. These localities are Glen Skiag in Ross, where, around a central nucleus of leucitoidal crystals of garnet, translucent quartz is arranged in layers which alternate with those of the garnet, conformably to the figure of its crystal.The two other localities are the first and third granitic veins to the east of Portsoy; in both of which garnet of a pale brown colour is laced with quartz, which is arranged in a graphic manner, as in the felspar from an adjacent vein. At no other locality do I know of such an occurrence. The appearance of a section of a rhombic dodecahedron is somewhat like the figure.

1. Chapters on the Mineralogy of Scotland. Chapter IV. Augite, Hornblende, and Serpentineous Change

A couple of months ago I had the honour of submitting to the Society a speculation upon the metamorphism of a particular rock mass. To-night I again return to metamorphism, submitting, however, not a speculation, but the closely elaborated process of the change which has affected another rock.

XVII.—Chapters on the Mineralogy of Scotland. Chapter Fourth.—Augite, Hornblende, and Serpentinous Change

Malacolite was first observed in Scotland by Dr Macculloch, who included it with the second sub-species, under the name of Sahlite.He, in his different works, noted its occurrence—“near the church of Rodel in Harris,”- “in Tiree,”-“Glen Elg,”-“Glen Tilt,”-and “in Rannoch.” With his usual power he describes the occurrence, varieties, and even the crystalline form of the mineral,—the clearness and precision of his descriptions being only equalled by the utter want of precision and frequent mystifications as to their localities.The above sentence conveys all the direct information which Dr Macculloch vouchsafes as to the five localities indicated by him, though in a vague manner he may occasionally lead one to conjecture that certain particular spots are meant.By the time that the mineralogist, led by Dr Macculloch to Glen Elg, Tiree, or Rannoch, has walked some twelve or twenty miles in an unsuccessful search, he begins to think that if he be successful, he has some claim to be himself regarded as an independent discoverer.

X.—Chapters on the Mineralogy of Scotland. Chapter Second.—The Felspars. Part I

Before submitting the results of my examination of the silicates, it is incumbent upon me to give an outline of the processes adopted for their analysis, seeing that the amount of confidence which is to be placed in the results must rest very immediately thereupon.1. Determination of the Water. — In all silicates which were found, after thorough drying, to give out moisture when heated in the closed tube, the amount of loss upon ignition was calculated as water. About 2 grammes, crushed in the diamond mortar, were first merely heated throughout in the air-chamber of a water-bath, the contact temperature of which was 212° Fahr., the temperature of the air-space being never below 199°. The weight after this heating was taken; and, except in the case of a mineral functioning in any peculiar way, the loss in weight was estimated as hygroscopic moisture. The mineral was now continuously heated in the bath until the weight was found to be constant. It was then exposed for the space of one hour to a full red heat, in the flame of a Bunsen burner, after which it was re-weighed. Finally, it was exposed for ten minutes to a heat approaching whiteness, in a three-jet Griffin blast-furnace, again re-weighed, and again heated in this furnace, until the weight was constant.