Friday 14 June 2024

Are these the fingerprints of the builders of Stonehenge?

Newall's Boulder is a small rhyloite joint block found at Stonehenge, transported there from Crag Rhosyfelin and now in Salisbury Museum which has many fascinating features, it is described at and in more detail at Bevins et al 2023 , and in various posts on this blog.

Photo of hands holding Newall's boulder from Dr Brian John

One of the stand out features is the presence of small Tufa growths on the surfaces, including the "fresh" broken surfaces which are presumed to be from after the block was brought to Stonehenge.

Tufa deposits are the white patches on the block. The block came from an acidic soil but in the chalk of Wessex deposits of Calcium Carbonate can grow. In our homes we know the curse of limescale. Tufa and limescale are both formed through the precipitation of calcium carbonate from water, but they differ in their formation environments and characteristics.

Details of Tufa deposits on part of the block

Microorganisms play a multifaceted significant role in the formation of tufa. Research suggests that diverse microbiota colonize tufas and actively participate in the rapid formation of these carbonate deposits. Pedley, H. & Rogerson, Mike. (2010). Introduction to tufas and speleothems. Geological Society, London, Special Publications. 336. 1-5. 10.1144/SP336.1.

Because the formation of tufa depends on many factors it is rare on buried blocks of stone in the chalk. They need air and water, a certain amount of warmth and usually an organic starter, which is sometimes incorporated in the deposit.

This tells us that the block was buried in loose chalk, the bases of the megaliths are in compacted chalk which are anaerobic, but the fill between them didn't need to be compacted. (I think where it was found was recorded)  And that is was contaminated by organic matter.

It is pure speculation but could that contamination be from the builders dirty fingers as they dumped the broken block?


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