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Chesil Beach -Introduction Page
Magnetite pebbles were first discovered on the Chesil Beach in recent years by Mr David Harvey, who discovered black magnetic pebbles at the Abbotsbury end of the Chesil Beach in the year 2000. With them were other pebbles apparently of magnetite which seemed to have no major effect on a compass. Associated are some pebbles of metamorphic rock, such as schist or gneiss. Magnetite, also known as lodestone, is not a material that would be expected on the Chesil Beach and thus the possibility of a shipwreck origin was investigated.
The black magnetite pebbles occur at about the low water mark at about 1200m southeast of the end of the Fleet Lagoon. The map reference is SY 578832. The photograph shows Ian West standing near the crest of the beach lined up with the pebble location on the foreshore. If a line is taken normal to the beach and lagoon at this point and is entended seaward this will fix the position of the main concentration of pebbles on the beach. The hill beyond the Fleet Lagoon here is Chesters Hill (northwestern part). (Incidental points about the photograph: 1. A notable feature of the Fleet Lagoon is that there are no cliffs at the back of it, that is on the landward side, and this suggests that the Chesil Beach has always protected the land behind as sea-level has risen. This is very obvious at this point, Chesters Hill, where only some minor slumping is seen in the Forest Marble of flaggy limestone and shale. 2. Notice how plastic debris is washed and blown over the crest of the beach. The driftwood shows that the waves swash over the top in storms. 3. Notice how some low vegetation is being to colonise the flat crest of the beach.)
Magnetite, magnetic iron ore, or lodestone (loadstone) is iron oxide, Fe
3
O
4
. It contains 72.4 % iron so it is a valuable ore of iron. There can be some small amount of replacement of iron by magnesium or titanium in some cases. The mineral belongs to the cubic system and is commonly as octahedra. There is a poor octahedral cleavage. The colour is iron-black. The streak is black and the lustre metallic or submetallic. The hardness is 5.5 to 6.5 on the Moh's Scale and it is notably of high density so that when pure it has an SG of 5.18.
Magnetite occurs as a primary constituent of most igneous rocks and is often present as minute crystals. Large deposits are considered to be the result of magmatic segregation, as in the Urals, and Northern Sweden, Kiruna, Gellivaare etc. Workable magnetite deposits occur also in lenses in metamorphic rocks, such as schists, as in the Adirondack belt in the eastern U.S.A. The pre-metamorphic nature of these deposits is a matter for discussion. Pyrometasomatic and contact-metamorphic (i.e. skarn) magnetite deposits are widespread but not of great importance in production. Magnetite is a constituent of many veins; it is found in residual clays, and in placer deposits - the "black sands" - formed by the degradation of earlier deposits. For more information on the mineral see Magnetite: The Mineral and Gemstone Kingdom.
Lodestone is magnetic magnetite. In historic times it was used to magnetise the soft iron wire in a compass card suspended at the centre of a vertical needle. The ships had to carry lodestone to remagnetise this wire. See the website: Navigation: The Mariner's Magnetic Compass.
Without lodestone the Chinese would not have invented the magnetic compass and the great voyages of discovery could hardly have taken place. Not all magnetite is magnetic (and it is not all magnetic here on the Chesil Beach). Lightning strikes of magnetite are believed to cause the iron oxide to become magnetic. For more information on this see the website The Loadstone .
The Pole Star (Polaris) served as the seaman's lodestar (or star that shows the way). Therefore the
magnetic stone which was used to magnetize the compass needle was called a lodestone. The magnetic,
direction-finding property of the lodestone had been discovered in China as early as the twelfth century.
By the sixteenth century, the mariner's compass was made with a soft iron wire bent to a lozenge shape and
attached to the underside of a circular compass card, which was suspended at the center on an upright
needle.
Because the iron wire tended to lose its magnetism over a period of time, it was necessary for each ship to
carry a good lodestone to re-magnetize the wire when it weakened.
Footnote: Use lodestone to attract a lover, but check whether it is male or female lodestone!
Lodestone: The Lucky Mojo Curio Company. Extracts: "Since ancient times, the lodestone has been held in high regard as a powerful amulet and all-around good luck charm because its magnetic influences are supposed to attract power, favors, love, money, and gifts.... Single large lodestones are used to draw money or luck, while paired "male" and "female" lodestones play a role in spells to attract a lover"
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The Magnetite Pebble Concentrations
These photographs are to provide a realistic impression of the beach at low tide in wet weather on the 18th of October, 2000. The conditions were those of a progessively subsiding strong wind, although not a storm, and continuing light drizzle blown in from the sea. The waves were of significant size, although not great for the Chesil Beach. The tide was low and the pebbles were easily found just over a kilometre from the end of the Fleet Lagoon. The beach changes and these pebbles may not be so clearly visible now. David Harvey and Ian West had walked southeast from the Dragon's Teeth (wartime concrete defences against German tanks) at Abbotsbury in the rain, and Mr Harvey soon found some isolated pebbles, which led him to the main exposure rich in magnetite, which was already well-know to him. It is worth noting that there are also black chert pebbles on the beach, that can be confused at first sight with the magnetite, but they are less dense, non-magnetic and cannot be scratched with steel. The pebbles are mostly present in the wet lower part of the beach in the left photograph from the camera to the figure. The ones at my feet (
incidently the Ian West hair style has been much admired and may become fashionable!) in the right photograph are fairly small, but numerous. There is also black magnetite sand, mixed in with brownish quartzose sand. Larger isolated magnetite pebbles (like those in the photographs with the compass) occur higher on the beach. They are scattered in this general area, but do not seem to be present at the top of the beach.
The source of the magnetite is a fascinating problem. The mineral does not occur in any significant quantity in the area, and the metamorphic rocks associated with it are not found near Dorset. It is true that the Chesil Beach contains material from southwest England, but any large source of magnetite there that could be naturally transported to this beach is not known. Quartzite pebbles like those of Budleigh Salterton are common in some parts of the Chesil Beach, but no large magnetite exposure has been found in east Devon, as far as the authors are aware. In any case, nearly all the Chesil Beach pebbles are of highly resistant, quartz-rich rocks and the magnetite is softer (hardness 5.5 to 6.5 on the Moh's Scale unlike quartz of 7). Furthermore, the magnetite pebbles are very localised and not widely distributed along the beach. Natural processes do not easily account for this accumulation. Thus, a possible shipwreck source was kindly investigated at our request by Gordon Le Pard of the Dorset Coast Forum, Dorchester.
Gordon Le Pard seached the Maritime Archaeological Record at Dorchester for a possible shipwreck which might have deposited the iron ore found on the Chesil Beach. He said that of the 141 wrecks that he has listed as having taken place on the Chesil Beach, only one is recorded as carrying iron ore. There may have been others because for more than half the wrecks, the cargo is not recorded or is given as general or mixed cargo.
The one wreck that certainly carried iron ore, according to Gordon Le Pard, is that of the Dorothea, which ran on the beach between Abbotsbury and Langton Herring on the 14th February, 1914. The location is about right. He reported that the ship was eventually salvaged, but this would have entailed removing the cargo to lighten the vessel. He commented that it would not be surprising if a substantial amount of iron ore was spilt on the beach as the cargo was transhipped. Mr Le Pard has kindly provided the photographs, shown above, which have been reproduced with minor retouching and light tinting. Here are some further notes from Mr Le Pard's collection. "When the steamer Dorothea, of Rotterdam, went ashore at Langton during the night of 14th/15th February 1914, the crew were able to walk ashore at low water." ...."One which caused a good deal of interest locally was that of the Dorothea, a large coaster carrying iron ore from Spain to Holland, which in February 1913 (?) was carried broadside on high up the beach at Abbotsbury where she remained high and dry from months. At last, when she had been almost despaired of, she was refloated during an exceptionally favourable tide." Caption to the right-hand side photograph above. "The Salvage vessel Lyons standing by the S.S. Dorothea, stranded on Chesil Beach in February, 1914." Note by Mr Le Pard of recollection of Mr Walter Bellamy. "..Mr Bellamy rescued two dogs from the wreck in a pillowcase, a pom. and a daschund. At Abbotsbury the captain's wife saw rabbits and said "rabbits" - the only English word she knew! Mr Bellamy said that the cargo was left on board."
Notes by Gordon Le Pard from the Dorset Year Book, 1969-70, pp. 105-106. "The Salvaging of the Dorothea". The vessel was after a time launched broadside down the beach, a clever piece of work carried out by a firm from Great Yarmouth. Baulks of timber were placed under her keel to form "ways" for her to slide down on. When a tier of baulks had been laid, two of our tugs would start towing, one on the bow and one on stern; when far enough down they repeated the operation with baulks and so on until she reached the water. Here they encountered bad luck, a strong wind sprang up, whipping up a nasty sea, which pounded her to such an extent that it buckled her plates and frames. Had the heavy weather continued they would probably have lost her, but fortunately the weather improved quickly and the next time towage was resumed she came off though with a rather nasty list. She was towed to safety, ballasted and put on even keel, then towed to a dock, repaired and eventually sold for a good figure." With the illustration of Dorothea and tug Lyons, shown above.
Report in the Southern Times, 12.02.1916. "Abbotsbury. End of the Dorothea. The s.s. Dorothea, which, it will be recollected, was stranded and lay on the Chesil Beach a little distance from here for so long two years ago, and which was eventually re-floated, has had an eventful career. After being thoroughly repaired she was sold to a firm to be used in the London Newcastle trade, and while on a voyage in the North Sea struck a mine and sank. The crew were saved."
In 1937 another ship that was carrying iron ore past this region was wrecked. That incident, however, was off the Isle of Wight. The 5,000 ton Italian steamer Luigi Accame was carrying iron ore from Algeria, and like the Dorothea, was also bound for Rotterdam (Medland, 1995). On April 6th, 1937, her siren was heard wailing in thick fog close to Rocken End. The coastguards fired warning rockets but to no avail. The Italian steamer ploughed onto the rocks three quarters of a mile west of St. Catherine's Lighthouse. The crew were rescued by lifeboat and eventually the ship was patched up and refloated. The bottom had been torn to shreds. It is not known whether the iron ore was magnetite and whether it is present on the sea-floor, or even on the beach here, as a consequence, but it is quite possible. The coast is shown in a photograph in Medland's book and this will give the position quite well.
Thus it seems probable that the rather unlucky ship, the S.S. Dorothea, was the source of the iron ore on the Chesil Beach near Abbotsbury. The magnetite ore seems to been covered by the beach shingle until the year 2000. It has been re-exposed by some natural removal of shingle from the front of the beach. The magnetite has a potential importance for tracing movement and behaviour patterns of pebbles on the Chesil Beach. The pebbles are easily recogisable and it could be tracked by magnetic methods. Furthermore, it is effectively coming from a point source.
This is only a preliminary report and it would be useful if further study was made.
We are very grateful to Gordon Le Pard of the Dorset Coast Forum for providing very helpful information and for copies of two of the photographs regarding the Dorothea shipwreck. His data comes from the Maritime Archaeological Record at County Hall, Dorchester, Dorset.
Please see also the reference list of the Chesil Beach - Introduction Page
Medland, J.C. 1995 (revised edition - previous edition 1986). Shipwrecks of the Wight. 70pp. ISBN 0 9511498 0 6. Coach House Publications Ltd., The Coach House, School Green Road, Freshwater, Isle of Wight, PO40 9BB.
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© 2007 Ian West and Tonya West. All rights reserved. This is a purely academic website and images and text may not be copied for publication or for use on other webpages or for any commercial activity. A reasonable number of images and some text may be used for non-commercial academic purposes, including field trip handouts, lectures, student projects, dissertations etc, providing source is acknowledged. No permission can be given for reproduction of any images of the Lulworth Cove area in books or in other websites, for special reasons.
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Webpage - written and produced by:
.
Ian West, M.Sc. Ph.D. F.G.S.