diopside

Updated: May 24, 2025

Whatever may be thought of the explanation here advanced of the laminated structure of the rocks of the trachytic series, I venture to call the attention of geologists to the simple fact, that in a body of rock at Ascension, undoubtedly of volcanic origin, layers often of extreme tenuity, quite straight, and parallel to each other, have been produced; some composed of distinct crystals of quartz and diopside, mingled with amorphous augitic specks and granular feldspar, others entirely composed of these black augitic specks, with granules of oxide of iron, and lastly, others formed of crystalline feldspar, in a more or less perfect state of purity, together with numerous crystals of feldspar, placed lengthways.

Charles Darwin - Volcanic Islands