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Source: https://nitter.net/CalMac_Updates/status/2064691623447965967#m

Despite v poor forecast, it turned out lovely for yesterday's Pebble Picnic event at Port a Churaich (aka Columba's Bay) , Iona.

It turned out that we had (by accident) chosen St Columba's Day for this visit to the beach, where he landed in his coracle in the year 563.

Iona pebbles have been a big part of local and visitor lore for at least hundreds of years, and probably longer.

I'll be running more Iona #PebblePicnic events on 14th July and 13th August.

#Iona #Pebbles #Lewisian #Geology

#ThinSectionThursday I've been thinking about lovely Lewisian rocks from the island of Iona today.

So here's a very weird Iona rock I collected a few years ago: marble with a large diopside crystal, showing intense stripy strain/shock lamellae in crossed polar light. something dramatic has happened to this rock (and to others nearby), but we don't know what, or when. So many mysteries....

Field of view 2mm wide. More info in Alt txt.

#Geology #Lewisian #Iona

Today I was given this fabulous rock specimen from the Lewisian Complex in Iona.

We have a grey banded garnet-gneiss on the left side of the image. This banding is truncated by the dark rock on the right, indicating that the dark rock must have been intruded after the banding had formed.

Then both rocks have been heated, and the grey banded rock has partially melted, forming a granitic melt which has then intruded into the dark rock.

More in Alt txt.

#Iona #Lewisian #GranuliteFacies