56 
THE BOND SPRINGS STONY METEORITE 
that these lamellae consist of a nickel-iron alloy somewhat 
richer in nickel than their kamacite host, which consists of 
a -iron; and they may be either residuals of y-iron from 
the y to a transformation, or possibly bodies of ai-iron 
into which it has recently been shown (1) that such -iron 
may change on cooling. 
PyrrJiotite. The pyrrhotite is creamy-brown in colour, 
magnetic, and polishes readily; it is slightly pleochroic and 
strongly anisotropic. With nitric acid, it is practically 
inert; a slight staining to a deeper brown results, but no 
effervescence or etching. Potassium hydroxide slowly stains 
the mineral dark brown ; hydrochloric acid, ferric chloride and 
mercuric chloride give negative results. The mineral is 
therefore pyrrhotite, not troilite. According to Short (10, 
p. 74) and Farnham (5, p, 121) troilite effervesces vigorously 
with both nitric and hydrochloric acids, gives off fumes of 
hydrogen sulphide, and the surface of the mineral is etched ; 
these results were confirmed by the authors for troilite in the 
Henbury Meteorite, Microchemical tests for nickel were 
negative. 
The fact that the iron sulphide is pyrrhotite, not troilite, 
runs counter to generally accepted ideas about iron sulphides 
in meteorites. Hodge-Smith (7, p. 46) writes:— “A sug- 
gestion was made by Rose that troilite might be the mineral 
present in the irons and pyrrhotite in the stones. But the 
work of Ramsay and others appears to show clearly that 
troilite is the mineral characteristic of meteorites, whether 
they be aerolites or siderites.” It is therefore significant 
that Stillwell (11) has also determined pyrrhotite in a stony 
meteorite from Caroline, South Australia, by microscopic 
examination of polished sections. Since determination of 
troilite in various stony meteorites appears seldom to be based 
on a microscopic examination by reflected light and chemical 
tests, the conception that troilite is the characteristic iron 
sulphide mineral of all meteorites is doubtful. 
Chromite. Occasional gray isotropic crystals which resist 
all standard etching reagents are present. The larger grains 
are generally irregular in outline, but some of them and 
several smaller grains about 50 microns across have well 
marked octahedral shapes. This mineral is probably chromite. 
It is associated with transparent rather than with other 
opaque minerals, but the fact that nickel-iron and pyrrhotite 
are occasionally moulded about such grains indicates that it 
crystallized earlier than these minerals. 
