Oddo, Chemisches Centralblatt, 1896, 228.) Acid calcium silicates are represented in the mineral kingdom by gyrolite, H2Ca2(S103)3 H20, a lime zeolite, sometimes regarded as an altered form of apophyllite, which is itself an acid calcium silicate containing an alkaline fluoride, by okenite, H2Ca(S103)2 H20, and by xonalite 4CaSiO 3 41 2 O.
Other black specks have been identified as haematite and ilmenite; gold has also been found; other included minerals recorded are rutile, topaz, quartz, pyrites, apophyllite, and green scales of chlorite (?).
Apophyllite and chlorite) may have been introduced along cracks.