Parent-Rock of the Diamond in. South Africa. 105 



composition, starting from them, and are sometimes 

 occupied by calcite. The pyroxene, under the micro- 

 scope, hardly differs from the one already described, 

 except tliat the green tint is slightly riclier and one or 

 two crystals contain tlie small dark brown negative 

 crystals, common in hypersthene and diallag. The 

 dominant cleavage, as before, is along the cliuopinacoid.^ 



The third mineral proves to be ati 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 moder- 

 ately pleochroic (phlogophite ?). It occurs generally in 

 plates, averaging about 0.1 inch long. The minerals 

 appear to have formed in the following order : {a) garnet, 

 (&jdiopside, (c) mica, (d) enstatite. As before, iron oxides 

 are very inconspicuous ; there may be a grain or two 

 (small) of serpentinised 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 rocks to the more 

 ordinary eclogites. The occurrence of a little mica indi- 

 cates the presence of a small amount of an alkali in the 

 magma. If necessary we may name it newlandite, but 

 personally I should prefer to call it an enstatite-eclogite, 

 for I think the coinage of fresh titles more often a bane 

 than a boon to science. -- 



5. This boulder is almost perfect, except that the gene- 

 ral 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 

 weathering of the minerals. Its girth, in three directions 

 at right angles, is approximately 20i in. by 19i in. by llh 

 in. It appears only to differ from the last-described in 



1 As noticed by Professor Lewis, lit supra, p. 22, in tlie iliopside, tlie ]irisni eleavnge 

 )ias practically disappeared, and a clinopinaeoidal cleavage re]ilaces tlie oiLho]iinacoiilal 

 usual in dialiage. 



