It is somewhat confusing at first sight that for pressure fringes, the object was chosen as the reference material and not the wall rock. In the previous cases we saw growth on one or two surfaces. These surfaces remained the same throughout the growth history. This happens when a vein forms from a succession of fractures that fill with vein material. These fractures can cut the host rock and vein at different locations and multiple fractures can be present at any given moment.
Stretched calcite veins in carbonaceous shale.
It is difficult to impossible to determine the sequence of fracturing. Individual stretched crystals span the whole width of veins. Tapley Hill Formation, Opaminda Creek, Arkaroola, South Australia. Width of view 3.8 mm, plane polarised light. Movies illustrating the formation of stretched veins.