I was recently asked by two friends of mine from the Suffolk Butterfly Survey to help identify a small collection of items they had found on a beach near Bawdsey. Among the items were a number of pieces of fossilised wood that evidently originated from a petrified forest that is known to exist in the area.
These fossils have been described to me as having been pyritized in the fossilisation process. This 'wood' now has the characteristics of a clinker-like substance being hard, heavy and metallic. Pieces of the specimens that have escaped pyritization are clearly light and woody. I understand, from the position of being an awful chemist, that the wood has undergone a chemical change by fossilising in contact with iron. Can I conclude that Iron Pyrites (ferrous sulphide) has been formed in these fossils? Since this mineral is a well known source of sulphuric acid and copperas described as a 'vitriol',I wondered if these fossils were perhaps the same thing as the raw material of the copperas industry which operated on the River Stour at Wrabness in the early 18th Century? As an ex-patriot of the Harwich area I know there was an ancient industry connected with the town that gave its name to a least two places along the River Stour: Copperas Wood is now an interesting local nature reserve and Copperas Bay is a significant feature of the river. I have it at the back of my mind that an enigmatic substance exists in local, tidal mud and that it produces weak sulphuric acid. In my youth I heard it rumoured locally that certain parts of the estuary were known where concentrations of the acid would attack metal fittings of moored craft. The potential for this corrosive substance seems to pervade the geology of all the local shores one way or another.
I hope that local historian, Leonard T. Weaver will have no objection to my reproducing the following extracts from his book 'The Harwich Story' (pp. 77-78) which was produced by the Harwich Printing company in 1975. In the part of the book I quote here, the author in turn quotes Daniel Defoe (of 'Robinson Crusoe' fame) writing in his book 'Tour Through the Eastern Counties' published in 1724 and Samuel Dale writing in 'The History and Antiquities of Harwich' published in 1732:-
He (Defoe) went on to say that the inhabitants of Harwich boast " that their town is walled and their streets paved with clay, and vet that one is as strong and the other as clean as those that are build or paved of stone. The fact is indeed true, for there is a sort of clay in the cliffs between the town and the beacon hill adjoining, which when it falls down into the sea, where it is beaten with the waves and the weather, turns gradually into stone..... These stones are gathered up to pave the streets and build the houses, and are indeed very hard". It was believed that the hardness was due to the petrifying powers of a spring which issued from the cliff (see Dale, p. 100).
The inhabitants called them "kidney" stones, and the streets were paved with them until the middle of the 19th Century.
The engraving of Harwich which faces page 18 of Dale's History shows boys gathering copperas stones which, with the gradual erosion of the cliff, fell on the beach or were exposed in the cliff face. The stones were taken to a Copperas House at Ramsey where, in the words of Dale (pp.111-12), "being mixed with earth and disposed into light Beds, it dissolves by the Rain from the Sky, which Water being by Trunks guided into a great cistern made of lead, from whence is conveyed into a boiler of lead, which having performed its operation upon it, produceth copperas, which is a sort of vitriol." No doubt the stones were taken up the Stour to Wrabness Wood beyond Ramsey where the water, impregnated with copper sulphate, was boiled in large leaden pans and after evaporation, was allowed to cool, forming crystals of blue vitriol, used for making ink and dyes.'
The area of the cliffs described were in the vicinity of what we know today as the Stone Pier. Large quantities of septaria were also removed from the same cliffs in the following century to produce Roman cement (p. 124). Septarian nodules are said to be very hard. Were these the 'kidney' stones used to cobble the roads of old Harwich? From the illustrations in the book (p.79) clearly a huge amount of material was surrendered to both the sea and industry in that area before the coast was secured by the original stone pier in 1850. These works had then become imperative to prevent the sea from reducing Harwich to an island! It may also be of some significance to my enquiry that sulphuric acid is a significant by-product of the process used to produce Portland cement, the ascendancy of which destroyed the Roman cement industry at Harwich (p. 126).
The 'goings on' of the M.0.D. in the woods at Wrabness in my lifetime were always shrouded in secrecy. It has left me with a lasting impression that this could be a place of historic intrigue. The more I learn about copperas, the more I sense there has been some ancient 'shenanigans' to lead journalists of the day and, ultimately, posterity, right up the proverbial 'garden path'. What alchemy took place at Wrabness to leave place names that would keep people like me guessing nearly 300 years later? Can we be sure what 'copperas' really was and how was it made? Was copperas stone pyritized wood, septarian nodules or something else?
I should be able to answer these simple questions, but the more I try, the more questions seem to be raised. Does anybody really know what this 'copperas' business was all about?