Hull Geological Society

Common urban rocks -

(a work in progress)

Larvikite and Lardolite

  Larvikite is an easily recognisable plutonic igneous rock. It is a syenite with large crystals the have a blue glimmer. The rock is mostly made of a feldspar mineral and contains no quartz. The blue colour comes from schillerisation - a bit like the interference colours that a geologist sees when looking at minerals with a microscope or those bright colours you see on the feathers of peacocks and some ducks. If you look closely you can see the cleavage in the crystals - faint lines of weakness.  There is a lighter blue version called "Blue Pearl" in ornamental stone trade and a darker "Emerald Pearl", which when weathered becomes almost black in overall colour. The rock comes from the Oslo Fjord area of Norway. It can be seen used as a gravestone or on shop fronts; it is often used for Marks and Spencer's and Burtons shops. Large blocks have also been brought on barges for use as rock armour to slow the rate of coastal erosion; you can see it at Withernsea and Sherringham.

Lardolite looks very similar but the overall general colour is brown.

Copyright - Mike Horne and Hull Geological Society 2020

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