20	THE MATRIX OF THE DIAMOND
	occurs in crystals or crystalline plates with the characteristic fine striation of enstatite, parallel to the vertical axis. It has a weaker double refraction than the other two minerals, its colours in polarised light being of the first order. It gives parallel extinction, and the cleavage plates show no hyperbolas. The plane of the optical axes is parallel to the cleavage. The colour is a paler green than that of the other two minerals. Before the blowpipe it is infusible, or nearly so. The specific gravity, as determined in Klein's cadmium solution, was 3.199. Maskelyne and Flight' have analysed loose fragments from the 'blue ground' of Du Toits Pan, as follows :—
	They draw attention to the resemblance of this bronzite to that in the meteorite of Breitenbach. If, with Tschermak,'2 we draw the line between bronzite and enstatite at a con­tent of 5 per cent, of iron protoxide, it will be seen that our mineral is just on that line; and thus, as having an intermediate composition, may be called with equal pro­priety either bronzite or enstatite. The bronzite sometimes alters into biotite, which may occur in it in scales or plates which appear to be secondary. It also alters into bastite, which often entirely replaces the bronzite, and may be quite an abundant constituent. Bastite is distinguished from bronzite by a faint yellowish colour,