Earlsferry's Mysterious Rocks

These rocks (or maybe peculiar stones) are a few that when I was a boy I picked up at about between the half and the low tide marks on the rocky part of Earlsferry's beach.  These strange rocks were special to me as I've found nowhere other than the Earlsferry beach where these came from. I have shown them to others at rock exhibition shows but no one that I talked to at these shows could shed any light as to what they are or how they came to be where I found them.

About every time that one or more of our family went looking for lobsters at low tides we'd pick up a few as curiosities and use them to line all of the pathways in the garden of our Earlsferry, home. These few I've always kept with me as another of my treasures and as they were the smallest ones that I ever found and are ones that I could carry with me. Most of the many round conical shaped ones that we found were several times the size of these two with the large end about lawn bowling ball size. 

The only place that I could reason that they came from was that they were volcanic bombs that were burped from the now topless volcano that we call Largo Law as part of a volcanic eruption that happened maybe several million years ago. Largo Law bears a remarkable similarity to the Mount St. Helens volcano in the USA's State of Washington which I witnessed as it blew its top on that Sunday morning in 1980.

What is interesting and special about the cone shaped ones is that they all are virtually the same  conical shape as what NASA developed as being the shape that a space capsule had to be to plunge from outer space and survive the fiery reentry through the atmosphere.

The other three rocks appear to be made of the same material as the cone shaped ones except that although they are indigenous to the same exact debris field as the conical ones they are flattish and with a strange pattern of white honey comb like segmentation throughout.

In mass all are dense and heavy and while I have tried to cut into one by the use of carborundum grinding wheels, all that I accomplished was the rapid wearing away of the grinding wheels. I am convinced that the only way to cut into one would be by the use of a diamond wheel.

Maybe someone who reads this will have another concept as to where these rocks came from and how they came to be scattered on to Earlsferry's, tide out, lower beach.

The fifth of October 2014.  Maybe the mystery is solved.

Retired geologist David Bursill who lives on the Isle of Skye writes,

Dear Mr. Reekie,

I have just spent a most enjoyable hour reading your website.   I am a Geologist and Lapidary, I cut gemstones.  Although I am now retired and living in the Isle of Skye, I spent my youth and middle years in Cambridge and was at The Department of Geology and Sedgwick Museum for twenty two years.

I have come across stones like your mysterious stones before at the Roslyn Pit in Ely  in the Fens.   They are nothing to do with volcanoes though, but are called Septarian Nodules. They are sedimentary structures that formed on a sea floor and were formed when organic matter, a fish perhaps, fell onto the sea floor and was rapidly covered by sediment. 

The organic goo partially decomposed and formed a sort of membrane enclosing the organic matter, because the goo inside was concentrated then osmotic pressure forced sea water through the membrane  causing it to swell, when eventually the pressures equalised, everything stopped and the normal sequence of fossilisation occurred.

A very small piece of organic matter could make quite a big nodule, and I have seen and collected them up to three feet across, and weighing several hundred pounds!  The white veins are Calcite and are formed during the fossilisation process.

Interestingly, the greatest number of these nodules are found in Coal deposits and associated shales.

I am most interested in the Elie Rubies deposit you mention and will certainly visit next year.