This Post describes Stones #7 to #9 of the 12 (Part One dealt with Stones #1 to #3 and Part Two with Stones #4 to #6):
7) Stone #7 Red-Stained Quartzite, found near Budleigh Salterton, England.
On two recent visits to England, in 2017 and 2018, I went to a coastal village of about 5,000 inhabitants called Budleigh Salterton in Devon, not far from Exeter. The Doomsday Book records that salt panning was of great importance here, and it may have been as far back as Roman or even Iron Age times, hence the origin of the name “Salterton”. The beach, three miles (nearly five kilometres) in length, has a distinctive mix of stones, many deriving from the Budleigh Salterton Pebble Bed which outcrops in the cliffs there.
The layers of pebbles found in the cliffs at Budleigh Salterton originated over 400 million years ago when sandstones formed under desert conditions in the place in France we now call Brittany. During the Triassic period, these rocks were eroded and transported by vast rivers across what later became the English Channel to form the Budleigh Salterton Pebble Beds. The pebbles then fell onto the beach and have been transported eastwards by the sea, well beyond Budleigh Salterton.
The East Devon and Dorset Coast, known as the Jurassic Coast, has become a World Heritage Site due to the geology of the area. In 95 miles (150 kms), 185 million years of earth history are on display in the coastal cliffs. Older Triassic rocks (between 251 million and 200 million years old) give way to Jurassic rocks (200 million to 145 million years old) and younger Cretaceous rocks (145 million to 66 million years old).
The British geologist Ian West has a very interesting web page on Budleigh Salterton and the surrounding area (even though it can be difficult to read in places). There he states that the dominant pebbles in the Budleigh Salterton Pebble Bed are quartzite (if you go to this link, click again on it to enlarge the writing at the bottom of the photo). Quartzite is a very hard durable metamorphic rock composed almost entirely of quartz. It forms when a quartz-rich sandstone is altered by the heat, pressure, and chemical activity of metamorphism. These conditions recrystallize the sand grains and the silica cement that binds them together. The result is a network of interlocking quartz grains of incredible strength. Impurities in Quartzite can cause it to be yellow, orange, brown, green, or blue. The presence of iron results in pink, purple or (as with Stone #7) red.
Location of Budleigh Salterton in south-west England (source: Google Maps):
8) Stone #8 White-Grey Quartzite.
I collected this stone at Birdlings Flat, Canterbury, a beach that I try to visit at least a couple of times each year because of the Quartzites, Jaspers and Agates (see Stone #11) to be found there. Birdlings Flat is the beach immediately south of Banks Peninsula, part of Kaitorete Spit, an enormous barrier gravel bank which lies between Lake Ellesmere and the sea. Stones washed down from the Alps by Canterbury rivers are swept northwards along the coast and deposited here.
As mentioned in relation to Stone #7, Quartzite is a very hard durable metamorphic rock composed almost entirely of quartz. Many different coloured Quartzite stones can be found at Birdlings Flat, as attested by the collection to be found at the Birdlings Flat Gemstone and Fossil Museum, which I have visited a number of times.
Stone #8 is one of a number of white-grey Quartzites I have found at Birdlings Flat. The large bands of white and grey provide a striking contrast, making this stone particularly attractive.
There are a number of previous TumbleStone Posts about Birdlings Flat. These include: Birdlings Flat Gemstone and Fossil Museum; Seven Types of Stones Collected at Birdlings Flat; Selection of Online Sources about Birdlings Flat; and Information on Birdlings Flat from Books.
Location of Birdlings Flat (source: Google Maps):
9) Stone #9 Unknown stone, found at Riverton.
I picked up this interesting little stone at Henderson Bay, Riverton Rocks. I initially wondered if it might be a piece of petrified wood, given its pattern and texture. Some agatised wood (see photos below) that I have seen has some similar patterns. Petrified wood forms when wood is buried by sediment and protected from decay by oxygen and organisms. Groundwater rich in dissolved solids flows through the sediment, replacing the original wood material with, for example, silica, calcite, or pyrite. Agatised wood has been petrified by agate, a form of chalcedony or microcrystalline quartz. However, the agatised wood I have seen tends to be quite glassy when polished, something absent from this stone.
In March 2017 I bought a piece of petrified wood from Hettie’s Rock and Crystal Shop in Akaroa on Banks Peninsula.
I have also seen petrified wood at Curio Bay, about 130 kms east of Riverton.
On the basis of what I have seen, I am unsure whether Stone #9 is agatised wood or some other form of petrified wood, or something entirely different. I have more unidentified stones than identified ones in my collection. [Later I came to the view that this stone is much more likely to be a mix of quartz and a black mineral, not any type of petrified wood.]
I found Stone #9 at Henderson Bay, the last of the Bays that make up Riverton Rocks, the part of Riverton that is made up of holiday homes. My grandparents owned a “crib” (“bach” to North Islanders of New Zealand) at Henderson Bay, up on the hill overlooking the sea, and when I was a boy my family spent two weeks every summer on holiday there.
Location of Henderson Bay and Back Beach, Riverton (source: Google Maps):
Part Four is the final Post in this series, dealing with Stones #10, #11 and #12.
4 thoughts on “Twelve Stones, Part Three”