Professor T. O. Bonney — Parent-roch of the Diamond. 315 



of a second more altered pyroxene. In thin slices the paler and 

 pinker tint of the garnet is very perceptible, as well as the tendency 

 to a rude and generally parallel cleavage. But we find in it, under 

 the microscope, a few microlithic enclosures, of au apparently colour- 

 less mineral, which occurs in long prisms crossed at about 70° by 

 an occasional transverse cleavage, and extinguishing at an angle 

 of about 26° with the longer edge. Many of the cracks exhibit 

 slight decomposition, starting from them, and are sometimes occupied 

 by calcite. The pyroxene, under the microscope, hardly difiers 

 from the one already described, except that the green tint is 

 slightly richer and one or two crystals contain the small dark 

 brown negative crystals, common in hypersthene and diallage. The 

 dominant cleavage, as before, is along the clinopinaco'id.^ The third 

 mineral proves to be an altered enstatite, but I leave the details 

 for the present as it is better preserved in another rock. A fourth 

 constituent is also present, but more sparingly, viz., a pale-brown 

 mica, only moderately pleocliroic (pljlogophite ?). It occurs generally 

 in plates, averaging about 04 in. long. The minerals appear to have 

 formed in the following order : (a) garnet, (fc) diopside, (c) mica, 

 (d) enstatite. As before, iron oxides are very inconspicuous ; there 

 may be a grain or two (small) of serjoentinised olivine. The marked 

 presence of enstatite distinguishes this rock from the others, but 

 it differs from the eulysites by the substitution of that mineral for 

 olivine, and so links those rucks to the more ordinary eclogites. 

 The occurrence of a little mica indicates the presence of a small 

 amount of an alkali in the magma. If necessary we may name it 

 newlandite, but personally 1 should prefer to call it an enstatite- 

 eclogite, for 1 think the coinage of fresh titles more often a bane 

 than a boon to science. 



5. This boulder is almost perfect, except that the general flatness 

 of one side indicates either traces of an old fracture or considerable 

 loss by crumbling. The surface has been smooth, but it has suffered 

 from unequal wea,thering of the minerals. Its girth, in three direc- 

 tions at right angles, is approximately 20^ in. by 19^ in. by 17^ in. 

 It appears only to differ from the last-described in having its garnets 

 a shade more purple, and in an approach to a banded structure ; the 

 diopside being rather more abundant in a middle zone, the garnet in 

 one, the enstatite in the other of the outer zones. Being satisfied 

 that it is merely a variety of the last-described rock, I have preferred 

 to leave it as an intact boulder. 



6. The next fragment, measuring about Sin, by 2|^in. hy 2 in., 

 and retaining part of its smooth outer surface, is labelled " found in 

 the yellow ground of No. 2 mine" 50 feet deep." Though it is 

 much more decomposed than the others, the purplish garnet, the 

 emerald-green pyroxene, the altered enstatite (here very rotten), 

 and a flake or two of phlogophite (?) are easily made out. It is 



' As noticed by Professor Lewis, ut supra, p. 22, in the diopside the prism 

 cleavage has practically disappeared, and a clinopiuacoidal cleavage replaces the 

 orthopinacoidal usual in diallage. 



* The others come from another mine (No 1). 



