360 
ME. N. STOEY-MASKELYNE ON THE 
when etched. The interspaces are partly filled by meteoric pyrites (troilite) in small 
patches, recognizable by its pinchbeck brown colour, the rest of the surface being occu- 
pied by a greenish and greyish-brown crystalline magma. It is of the ingredients of the 
last-mentioned portion of the meteorite that I shall first speak. On treating the whole 
mass with mercuric chloride at 100° for some hours the iron and the troilite are dissolved, 
and the magma before alluded to remains unattacked. But it has now lost its compound 
structure, and is found to consist of three substances : — 1, highly crystalline, bright green, 
or else greenish-yellow grains ; 2, rusty brown, sometimes nearly black, sometimes also 
nearly colourless grains of a mineral that presents crystalline features, but on which 
definite crystalline planes are of great rarity ; and 3, crystalline grains of chromite. 
The first of these three minerals proved to be a ferriferous enstatite, or bronzite, the 
second is a mineral to which I do not at present assign a name, for it corresponds in all 
respects, except its crystalline form, with the tridymite of Professor Vom Rath. In 
respect of their forms, however, it is difficult to suppose that the two minerals are 
identical. 
XIII. Bronzite of the Breitenbach Siderolite. 
My friend Professor Von Lang measured crystals of the bronzite of the Breitenbach 
meteorite at the British Museum so long ago as 1863, and during last year he published 
his results *, — results that were mineralogically important as affording for the first time 
satisfactory and complete data for the crystallography of a rhombic mineral with the 
formula of an enstatite. This investigation was made exceptionally difficult by the 
very partially developed or merohedral character of the crystals on which Professor 
Von Lang had to experiment. A similar difficulty attended the crystallography of the 
silica of this meteorite. I need only recapitulate of Dr. Von Lang’s results the elements 
and some of the important angles of the crystal. 
Elements : — a: b : c=0-89568 : 0-84960 : 1, 
which give the following angles by calculation : — 
110.010 = 44° 8 
101.100 = 41 11 
011.010 = 40 16 
The mineral often presents itself in little spherules, invariably green in their tint and 
crystalline in their structure, as revealed by their optical characters, and sometimes, but 
very rarely, carrying here and there a crystal face. In fact the faces thus presenting 
themselves seem to do so almost fortuitously, and on the grains, which present a nearer 
approach to a true crystalline superficies, the faces that are developed exhibit very little 
of the symmetrical correspondence with other faces, or of the prevalence of those of any 
special forms, such as is ordinarily met with in crystals. 
The specific gravity of this mineral is 3-238, that of the silicates in the Steinbach 
siderolite, as determined by Stromeyer, having been 3-276, and as estimated by Rumler 
3-23. The hardness is 6. 
* Berieht der Akad. Wiss. Wien, Bd. 59, ii. p. 848. 
