Natural nickel-iron alloys have been found in several places on the earth's surface. In addition to alloys containing a low percentage of nickel (about 3%), there are others which contain much higher percentages of nickel (about 70%). To alloys of the latter group the name awaruite is now generally given and it may include josephinite, souesite, and other alloys possessing high nickel content so long as they belong to the same phase and possess identical crystal-structures.

It is of interest to the mineralogist to know whether these alloys conform to the structure of nickel-iron alloys prepared in the laboratory and whether they fit into the accepted phase diagram of the nickel-iron system. It is of interest also to the physicist and the metallurgist to obtain information concerning these natural alloys, because some nickel-iron alloys made in the laboratory are difficult to prepare in a state of true equilibrium. Data derived from the study of the natural alloys may help to throw light upon the structure of these artificial alloys.

Nickel-Speiss (Nickelspeise), an impure arsenide of nickel obtained as a by-product in the manufacture of smalt, has long been known as a source of distinct crystals representing a definite chemical compound. Such crystals were already analysed by Döbereiner (1823), who concluded that the material was an artificial form of niccolite, NiAS. Later analyses showed that the composition of the crystallized furnace product approaches Ni3As2, a compound unknown in nature at that time.

A substance corresponding to the crystallized nickel-speiss, but thought to be of natural origin, was first described by Breithaupt (1841), who named the material Plakodin (πλăκώδης, broad) in allusion to the tabular habit of the crystals. These were said to have occurred in the Jungfer mine at Müsen in Westphalia, associated with chalybite and gersdorffite and to have been salved by a smalt-works official from a shipment of ores.

The determination of the specific gravity of a solid which is only available in small quantity has always been a difficult problem in cases where the suspension method fails, either because the solid is too dense, or because it dissolves in or reacts with the heavy liquids available. It is hoped that the following method will be found a useful addition to the numerous methods which have been proposed from time to time to meet such cases. References to most of these methods are given at the end of the paper. Neither the new method nor any one of the older ones is universally applicable, and the best method for any particular case will depend on many circumstances.

In December 1933 Major W. A. Pover, who was then ‘Iraq Public Works Department Executive Engineer of the Mosul and Kirkuk Liwas, showed the writer a portion of a meteoritic stone. This had been in his office doing duty as a paper-weight since it was brought to him by two of his men shortly after its fall.

At that time Major Pover was in camp, supervising the erection of the permanent steel road bridge that spans the river valley some five kilometres upstream of Tauq village. His men told him that the meteorite fell in the middle of the night; it was likened by those who saw it to the moon falling, and people were awakened by the jolt of its fall. When the morning came, some of his men went out to seek it, and they in fact found it. They described it as about two and a half feet in diameter, and they broke it up with a sledge hammer, when the fragments were eagerly collected by those who happened to be present. A portion they themselves took to Major Pover.

The existence of an unidentified mineral in the riebeckite-microgranite of Mynydd Mawr has been known for almost exactly fifty years. It was first noticed by Harker and described by him in the following words: ‘The ground-mass [of the microgranite] is a finely granular admixture of quartz and orthoclase, as in an ordinary “microgranite”, but containing in addition another mineral which is often plentiful. It occurs in minute crystals of acicular or rectangular form, scattered through the ground-mass or included by the other constituents, and having usually a fluxional arrangement agreeing with that of the parallel hornblende and tourma]ine streams. The mineral is colourless, or in the larger crystals gives for vibrations parallel to the long axis a faint tint of indigo-blue. The crystals give high polarisation colours and straight, or nearly straight, extinction. They have a high refractive index, which causes them to stand out in relief when viewed by ordinary transmitted light.’

Some time ago, Mr. F. C. Partridge, Mineralogist to the Geological Survey of South Africa, gave me some crystals of sapphirinc which he thought might be of interest for goniometric examination. They come from the farm Blinkwater 1037, about 47 miles NNW. of Pietersburg and 45 miles WSW. of Louis Trichardt in northern Transvaal, and were collected by him in July 1930, after he had identified some specimens of sapphirine sent to him by Mr. A. Ruskovitch of Abrasive, northern Transvaal. They occur in a coarse granitic rock rich in brown mica, and are associated with small prismatic crystals of pink corundum.

The sapphirine crystals are almost invariably tabular or platy in habit, although occasional crystals possess a rhomb-shaped cross-section. The largest crystal measures 50×35×5 mm., while the thickest one is only 7 mm. in thickness. They are generally six-sided in outline with a strong suggestion of orthorhombic symmetry.

Scawtite was first described at Scawt Hill as a secondary mineral occurring in vesicles and venules in melilite of a melilite-rich hybrid of the endogenous contact-zone. Since then scawtite has been identified in a gehlenite-vesuvianite-ealcite-rock from the contact-zone of a gabbro in the Little Belt Mountains, Montana. The present note records a further occurrence of scawtite at Scawt Hill in a different patagenesis, viz. in association with and replacing spurrite of the exogenous contact-zone.