Note 329 — Chapter XLIII · THE BOSSES AND SHEETS OF GABBRO
Reading edition
Zeitschr. Deutsch. Geol. Gesellsch. xxiii. (1871), p. 59.
[330] Professor Judd (Quart. Jour. Geol. Soc. xlii. p. 62) believes that originally all the gabbros contained olivine, and that where it is now absent, it has been altered into magnetite or serpentine. But in some coarse massive gabbros this mineral does not appear to have been an essential constituent. See op. cit. vol. l. p. 654.
[331] Op. cit. xli. In a later paper he insists on the gradation of the coarse granitoid varieties (gabbros) into holocrystalline compounds, where the felspar appears in lath-shapes with crystals or rounded grains of augite and olivine (dolerites), and thence into true basalts, magma-basalts, and tachylytes (op. cit. xlii. p. 62).