Metamorphism changing rock (new minerals + textures) without melting it often result in new mineral assemblage gabbro ampphibolite eclogite. Causes stress: deviatoric ~100 bar heat: geothermal 100-800c chemically active uids e. g. hot water ? veins typical features new mineral assemblages solid state di usion + rearrangement often loss of water/co2. Index minerals appear as porphyroblasts some are important gemstones changes in texture recrystallization (increase in grain size + interlocking mineral grains) sandstone (rounded grains) > quartzite (interlocking grains) Metamorphic fabrics geometric arrangement of features like mineral grains, class, compositional layers, planes of parting. Lineation one dimension caused by movement, intersecting planes (e. g. bedding intersecting cleavage), stretched pebbles. Boudinage stretching of relatively strong layers which break apart boudines rigid tablets embedded in weaker matrix competent rock layers stretched into segments often regular, but can be asymmetric. Volcanic structures on maps from the dike towards the centre.