70 MEMOIRS OF THE QUEENSLAND MUSEUM. 
The relationship between the structure as revealed by etching polished 
surfaces and the percentage of nickel has been well established by 0. C. 
Farrington and adopted by G. P. Prior 8 and others. 
The cubic irons or hexahedrites have an iron to nickel ratio greater than 
13 : 1. while the octahedral irons or octahedrites which constitute the main 
bulk of the meteoric irons range between 13:1 and 6:1. 
The Glenormiston iron with its ratio of 10-3 : 1 is, therefore, in the 
group of octahedrites on this basis, and one might expect it to show the 
minerals and structures characteristic of that placing. On etching a polished 
surface, however, one does not obtain the Widmanstatten structure so 
characteristic of the octahedrites, but instead there is developed the structures 
shown in the cubic irons or hexahedrites. The fact that the meteorite is so 
definitely brecciated may account for this. 
On the iron-nickel ratio the Glenormiston meteorite is a medium 
octahedrite. 
Examination of the figures in Plate VI will show the uneven distribution 
of the troilite, schreibersite, and the tsenite throughout the main mass of kama- 
cite crystals, and the borings analysed may perhaps be not truly representative 
of the mass as a whole. The correct sampling for analysis of a brecciated iron 
meteorite of this type is a very difficult matter unless an undue quantity of 
material is dissolved. 
Examination of Polished and Etched Surfaces. 
Structures and Minerals present. 
The meteorite is distinctly tough and the extreme labour and slowness 
associated with even quite small cuts with a hacksaw pointed to a rather 
high carbon content in the material. By means of a carborundum saw a face 
oi inches long and 3 inches wide was obtained and subsequently polished. 
This was cut from one end of the meteorite as shown in Plate III. 
The polished surface showed clearly the brecciated character and angular 
eutectic intergrowths of tsenite and plessite could be seen in reflected light, while 
small nodules of troilite and larger nodular masses of schreibersite alone or mixtures 
of schreibersite and troilite could be detected by the use of reflected light without 
magnification and without artificial aid (see Plate VI). 
The surface responded very readily to attack by dilute nitric acid ; the 
troilite nodules became dissolved leaving small rounded pits. The crystals of 
kamacite showed very well indeed the Neumann lines,, while the angular platy 
intergrowths of tsenite (and plessite) stood out in relief from the surface of the 
kamacite as it dissolved away. A beautiful damascene effect on some of the 
kamacite faces showed up in parts of the etched surface in the early stage of 
the attack and before the Neumann lines had been very w'ell developed. 
Miner. Mag., vol. xix. 
