The specimen studied weighs around 4.5kg; its form is that of a flat parallelopiped whose largest face measures 16cm x 9.5cm. The periphery is black, uneven and pitted by irregular cavities that are probably the result of the corrosion of pre-existing copules.

A predominantly metallic iron mass is peppered with tiny stony specks, which are irregular as to form and dimensions. Moreover, a few large fragments of rhombic, yellow pyroxene crystals attaining dimensions of 4cm x 2.5cm, occur, in addition to stony inclusions, of which one, measuring 4cm x 3.5cm, shows a brecciated structure.

The latter is present in the form of discontinuous grains and as anastomosing veinlets joining into a continuous border of the same metal that encloses large silicate fragments that cut across the fine grain of the remainder of the mass. This network of veinlets terminates abruptly at the edges, indicating that the latter had its present constitution before becoming apart from the principal mass.

An examination under a magnifying glass shows that in the silicate portions the metallic iron is accompanied by pyrrhotite, and this mineral is concentrated between the silicates and the iron. A small quantity of schreibersite also is present.

Here and there in the principal mass, the proportion of iron increases, and elliptical areas result. These measure up to 3cm x 2cm. These areas are heterogeneous and contain small inclusions of pyrrhotite in the central portions, whereas primarily silicates are present around their peripheries.

The metallographic study of all the modalities of the iron shows that it is itself heterogeneous, being composed of two nickeliferous alloys. The principal alloy is a form of kamacite. It is the softer and more soluble of the two and forms a conspicuous and continuous sheath about the silicates. Throughout this sheath, there appears, in the form of sinuous arabesques with curvilinear contours, a second alloy that is harder and more resistant. This alloy turns yellow upon exposure to the air and appears to be made up of taenite.

The great difficulty in sawing this mass of iron did not permit me to obtain proper sections for microscopic study of the silicate portion in the metal; it was necessary to be satisfied with isolating this portion chemically. The nickel-iron was eliminated by the action of a solution of copper and potassium chloride, the residue consisting essentially of a rhombic pyroxene associated with pyrrhotite, a small amount of schreibersite and a very small amount of olivine.

Three experiments were made on pieces weighing from 7 to 10 grammes. The silicate residue was, respectively, 12, 20 and 28 parts per hundred. The results of the metallic portion show it was 89.03 per cent nickel-iron, 10.38 per cent pyrrhotite and 0.51 per cent schreibersite. The composition of the silicate portion shows it was 8.7 per cent feldspars, 86.8 per cent hypersthene and 4.5 per cent peridot. A second analysis made upon another fragment gave a tenor higher in peridot; this shows that the various silicates are irregularly distributed.

The results show that if one takes a mean tenor for the silicates of 20 per 100 for the entire meteorite, it must be admitted that the Chinguetti meteorite constitutes a type of siderite differing from all those known.