Gieseckite

The persevering researches of Sir Charles Giesecke, in Greenland, have been productive of several new and many rare Minerals, some of which a less intelligent Mineralogist would have passed over. The fortune of war had for some time deprived him of the honour due to his discoveries; but now his merit is every where fully admitted. By way of perpetuating his name in the list of persons who have made themselves conspicuous in science, it is desirable to name some mineral after him, and we would propose the substance before us, as it appears to be quite new, and was brought by him from Akulliarasiarsuk in North Greenland. It occurs crystallized in hexahedral prisms imbedded in a claystone Porphyry, accompanied by a few crystals of red Feldspar. The crystals are usually solitary, though two or three are sometimes attached together: two of their sides are constantly wider than the remaining four; the angles measure 120°. They break easily with an uneven shining surface and blunt edges, without shewing any tendency to a foliated structure: the lustre is dull, rather waxy, and they are possessed of some transparency: the colour is olive green, varying in intensity to almost black: the hardness is between Fluor and Calcareous Spar. When heated this substance hardens, loses its colour, and with some difficulty may be fused into an opaque enamel. The sp. grav. taken from a crystal of an intermediate colour, was found to be 2.787.

The mineral nearest related to Giesechite is Finite, but that is infusible, opaque, has a foliated fracture, and higher sp. grav.

It is to be hoped, that Sir Charles Giesecke, or some eminent chemist, will favour the scientific world with an analysis, and fatter mineralogical description than we have been able to compile from the few specimens which were in the possession of Mr. Ileuland, that have come under our inspection. The one figured is placed in the cabinet of the Countess of Aylesford; it is illustrative of all the characters, except the size of the crystals, which is sometimes much greater.