Figure F4. Representation of textures developed in fine-grained mafic rocks. A. In this sample the white plagioclase crystals define a through-going network in which the mafic minerals occur intergrown with plagioclase. B. In this sample the plagioclase is uniformly distributed in a felty or jack-straw pattern. The texture in A is developed under more slowly cooled conditions and so is distinguished as a microgabbro, whereas the texture in B is indicative of rapid cooling to form a diabase.

Figure F4. Representation of textures developed in fine-grained mafic rocks. A. In this sample the white plagioclase crystals define a through-going network in which the mafic minerals occur intergrown with plagioclase. B. In this sample the plagioclase is uniformly distributed in a felty or jack-straw pattern. The texture in A is developed under more slowly cooled conditions and so is distinguished as a microgabbro, whereas the texture in B is indicative of rapid cooling to form a diabase.