(or pseudomorphs of alteration minerals after olivine) or pyroxene which give the rock a bladed appearance especially on a weathered surface. Spinifex texture is the result of rapid crystallization of highly magnesian liquid in the thermal gradient at the margin of the flow or sill. Harrisite texture, first described from intrusive rocks (not komatiites) at Harris Bay on the island of Rùm in Scotland, is formed by nucleation of crystals on the floor of a magma chamber. Harrisites are known to form megacrystal aggregates of pyroxene and olivine up to 1 metre in length. Harrisite texture is found in some very thick lava flows of komatiite, for example in the Norseman-Wiluna Greenstone Belt of Western Australia, in which crystallization of cumulates has occurred. Volcanology Komatiite volcano morphology is interpreted to have the general form and structure of a shield volcano, typical of most large basalt edifices, as the magmatic event which forms komatiites erupts less magnesian materials. However, the initial flux of the most magnesian magmas is interpreted to form a channelised flow facie, which is envisioned as a fissure vent releasing highly fluid komatiitic lava onto the surface. This then flows outwards from the vent fissure, concentrating into topographical lows, and forming channel environments composed of high MgO olivine adcumulate flanked by a 'sheeted flow facies' aprons of lower MgO olivine and pyroxene thin-flow spinifex sheets. The typical komatiite lava flow has six stratigraphically related elements; A1 – pillowed and variolitic chilled flow top, often grading and transitional with sediment A2 – Zone of quickly chilled, feathery acicular olivine-clinopyroxene-glass representing a chilled margin on the top of the flow unit A3 – Olivine spinifex sequence composed of sheaf and book-like olivine spinifex, representing a downward-growing crystal accumulation on the flow top B1 – Olivine mesocumulate to orthocumulate, representing a harrisite grown in flowing liquid melt B2 – Olivine adcumulate composed of >93% interlocking equant olivine crystals B3 – Lower chill margin composed of olivine adcumulate to mesocumulate, with finer grain size. Individual flow units may not be entirely preserved, as subsequent flow units may thermally erode the A zone spinifex flows. In the distal thin flow facies, B zones are poorly developed to absent, as not enough through-flowing liquid existed to grow the adcumulate. The channel and sheeted flows are then covered by high-magnesian basalts and tholeiitic basalts as the volcanic event evolves to less magnesian compositions. The subsequent