Sandstone is a common sedimentary rock, made up of sand sized grains of minerals and rock. Sand is eroded or moved from an area into an environment where sandstone might form (like a beach). Once enough sand has gathered together, the weight of layer upon layer of sand starts a process called diagenesis which results in the rock being compacted together and lithified, turning it into a rock! Diagenesis can occur from multiple processes, such as tectonic influences (fault lines crushing and compacting the sand), microbial activity and burying, increasing the pressure and temperature of the environment.

Sand is most commonly a cream to yellowish colour, but as we know in Aotearoa, there are other colours to be found, like black sand and red sand. Sandstones can be all sorts of colours, depending on the sediment that made them, processes they have undergone and what minerals they contain. Different sands can also be present within the same rock, creating bands or layers of different colours to create beautiful stripey rocks.