41. The Morgan Trail is a brownish-black to olive-black fissile siliceous pyritic shale. 42. This ore was pinkish and has been described as " compact, coarse, siliceous ". 43. It is common and characteristic of siliceous rock in interior valley and western mountains of California. 44. Sponge skeletons consist of either spongin or calcareous and siliceous spicules with some collagen molecules interspersed. 45. The rocks contain considerably more sodium and alumina than almost all Central Andes siliceous volcanic rocks. 46. In sponges they secrete calcareous or siliceous spicules which are found in the mesohyl layer of sponges. 47. In both localities, " B . epica " occurs among siliceous sand over limestone. 48. The Scots pine plays the same part in the other peninsular mountains, both siliceous and limy. 49. Underclay, which consists of siliceous refractory clay rich in hydrous aluminium silicates, is also called fireclay. 50. Pelagic sediments, containing significant quantities of siliceous biogenic remains, are commonly referred to as siliceous ooze.
