CHARACTERISTICS OF BASALTIC SEDIMENTS DEPOSITED IN A VARIETY OF GEOLOGIC ENVIRONMENTS ON HAWAII
The chemical stability of terrestrial felsic sediments can be arranged in a sequential order that essentially reflects Bowen’s Reaction Series. For example, olivine is the most labile whereas quartz, tourmaline and zircon are the most stable. For basaltic sediments, we propose applying the mineral paragenesis table derived by Wright and Okamura (1977) by sampling the Makaopuhi lava lake in Hawaii over time. Their table 15 presents the following minerals that crystalized at progressively decreasing temperatures:
The more stable minerals crystalize at lower temperatures. Vitric fragments, which are a common constituent in basaltic sediments, would be the most labile, while lithic fragments would be the most stable. Lithic fragments of basalt share many of the same properties of quartz crystals. Quartz has a hardness of 7, a specific gravity of 2.6, and fractures conchoidally. Basalt has a hardness of 6, a specific gravity of 2.8-3.0, and also fracture conchoidally. However, quartz is anisotropic and basalt is isotropic. We will show examples as to how this difference influences the grain shape and surface texture of basaltic sediments.