Thedark coloured rock is a sedimentary rock and the bright coloured rock is anigneous rock (used to

Thedark coloured rock is a sedimentary rock and the bright coloured rock is anigneous rock (used to be a magma) which intruded the sedimentary rock. This intrusiveigneous rock is called dyke or dike.This dyke is bright coloured because the minerals that makeup this rocks are breaking down to clays due to exposure to water and oxygen.Original minerals in rocks such as this one are usually black and so dykesoften appear dark (but, definitely not a rule!). However, when these mineralsbreakdown they produce clay minerals, which are usually bright coloured.The white-orange marks that you can see on the close-up image of thedyke used to be minerals that floated in the magma before it turned into a igneousrock. These minerals were called plagioclase, however, now these too have beenconverted into clays.You might notice that approximately all these tabular minerals arealigned in one up-down direction. This the tell-tale sign of magma movementwhich aligned the mineral according to its flow direction. From this photographyou can narrow down the magma movement direction options to either to up-downand towards-you/away-from-you.Southcoast NSW, Australia -- source link

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