Athough the pebbles of the shingle beach at Ringstead in Dorset first look much of a muchness, a closer inspection reveals that they have different characteristics and geological origins. I collected together some small groups of different types of pebble when I was last down on the beach and these are shown in the following photographs.
The majority of the pebbles are medium to large (almost cobble-sized), irregular, knobbly, flints like the white-coated ones shown immediately above and below. The natural dark grey or black colour of the glassy matrix shows through where the coating is chipped. The matt, powdery, white coating can get stained a rusty colour if the pebbles get buried deep in the sediments for a while. The dusty coating forms from the constant abrasion of one stone against another as the pebbles are moved around the beach by the waves.
Some types of pebbles are rusty-orange, browns or reds with a grainy, sand-like texture. They have a porous surface and white inclusions. Others are dark grey, even purple-grey or dark red. I wish I could tell you exactly what kind of rock they are made from. Unfortunately, the rock strata in the cliff along the stretch of coastline from White Nothe to Osmington Mills via Ringstead Bay is extremely varied and complex. I have been unable to determine with any confidence the real nature of the different pebble types.
For anyone desperately wanting to find out what rocks these pebbles are, may I suggest reference to Ian West’s web site on the geology of this area, which gives a full account of the stratigraphy and fossils.
Revision of a post first published 26 October 2009
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Jessica's Nature Blog 
The white ones look like sea softened bone fragments. I love the richness of the colours both in the close-up of the pebbles and the view of the shore.
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Thanks, Amy-Lynn. They do look a bit like worn bones, don’t they? One white flint in the middle of the arrangement even looks a bit skull-like.
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What’s extra-interesting to me is how many of these look like stones you might find here on our Lake Michigan beaches. Very, very similar. And I always wonder if some (not all, I’m sure) of the dark red ones might be remnants of old bricks, worn smooth by years in the water.
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I’m sure you’re correct in detecting a great similarity between the stones we find here and those near Lake Michigan. It might warrant a bit of investigation on my part to find out exactly how geologically similar the two areas are.
It is also true that some red pebbles can be water-worn fragments of brick – however, these have a very distinct texture, weight and wear pattern. The red pebbles in my pictures are not brick but stone. We have a great variety of rock strata and rock colours on the Dorset coast from the Triassic, Jurassic and Cretaceous periods of the Mesozoic era. Next time I’m on the seashore I’ll look out some brick pebbles and photograph them for comparison.
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More delights for my little geologist. He thinks you send him all these personally. He’s looking forward to meeting you one day on one of your beaches, so that you can show him “your best rocks” 🙂
Kind regards
Mark
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Hello, Mark
It would be lovely to spend some time rock-hunting on the beach with your little geologist one day. You must let me know if you are visiting the UK and perhaps we can arrange to meet up. It’s nice to have such an enthusiastic reader for my pebble, rock and shell posts.
Best wishes
Jessica
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I was brought up a mile from Ringstead Bay – recognise that shingle anywhere! Lovely
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Thanks for the comment, Juliet. I wonder whether the beautiful colours, textures and shapes of the Ringstead pebbles influence your pottery work at all – along with the other natural inspirations. Your sea urchin pots are delightful. Your glazes, especially the blue-green ones, are exquisite.
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Thanks. Definitely a strong influence. I have early memories of playing with the rusty streaked clay that we found on the beach as kids. Also mackerel fishing off the beach in Dad’s old dinghy – staring down through the blue water and the yellowy brown seaweed.
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The clay at Ringstead is special. It is the ‘home’ in which the beds of fossil oysters lie. And I sometimes find that lumps of it have broken loose and become rounded by rolling to and fro with the tide, gradually getting encrusted with yellow gravel so that they end up looking like those toffee apples covered with hundreds and thousands.
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Now that you’ve mentioned them I remember them clearly. It was a great place to grow up. I’m loving your blog by the way – although we’re coming from different points we have a very similar taste in the things we find interesting on beaches.
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