“Between the ocean and where they stood, drifts of smooth pebbles lay on the sand… gleaming from their recent dousing of sea water. All colours – red, glassy-white, cream, brown, black, speckled, clear green, pale green, dark green… They could hear the clatter of stones inside the belly of each wave as it rushed towards the shore.” (From page 39 of “Craggan Dhu: Time Will Tell” by Kay Cooke, a book inspired by the history, people and environment of Orepuki, a small town of New Zealand’s coastal Western Southland)
Stones from one country, gathered and tumbled, then going to another, nearly 15,000 kilometres away, across the Pacific Ocean.
I recently received an email from Sheila who lives in New Hampshire in the north-eastern United States (see maps above). Google says that this small State, one of the 13 colonies that rebelled against British rule during the American Revolution, is nowadays defined by its quaint towns and large expanses of wilderness. Commonly known as the Granite State, New Hampshire has extensive granite formations although schist is also significant in its geology. Sheila has an interest in smaller rocks. She wrote in her email:
I have a bunch of friends who aren’t rock-hounds per se, meaning they aren’t collecting specimens, but who just like pretty rocks with a bit of story to them, so I’m looking for small rocks with interest and character that would comfortably fit inside a closed hand that I can randomly send to people in the mail. (Our mottoes are “All Rocks Are Good Rocks” and “Whimsical When Bored”). A selection such as you would provide to a museum for counter displays to spark interest in children would be wonderful. Frankly you could just box up some raw rocks from the beaches and send them my way, and I’d be delighted, so long as I knew which beach was the source! Or you could send me stones that the tumbler rejected (ie didn’t take a good polish), or stones that you took out of your horses feet (with a note about whose foot it was).
Sheila also attached to her email some photos from TumbleStone Blog of stones that she liked. This gave me a good idea of what kinds of stones I could send her.
I have picked out 30 stones to send Sheila, ten each from three New Zealand beaches (Gemstone Beach, Kakanui and Birdlings Flat). The first ten come from the beach that Kay Cooke refers to in the extract from “Craggan Dhu” (above, at the beginning of this Post), Gemstone Beach, near Orepuki. It is the southernmost of the three beaches, situated on Foveaux Strait at the bottom of the South Island (circled in blue on the map of the South Island below). For more detailed account of stone collecting on Gemstone Beach, see here.
The ten stones from Gemstone Beach include three trace fossil argillite stones (see photos below). Trace fossils, also called ichno-fossils, are the fossilised marks, tracks, burrows and deposits of animals. There is a great diversity of trace shapes to be found in these green-grey stones, along with variations in size and colour. These traces were left in argillite rock about 250 million years ago, in the Permian Era, by the activities of ancient worms at the bottom of the ocean. Argillite is a hardened partly-recrystallised mudstone formed from ocean floor sediments. In the south of New Zealand, the ocean floor was uplifted by massive geological forces and the argillite was faulted and fragmented. Some of these fragments were carried out of eastern Fiordland by streams into the Waiau River then into Foveaux Strait, some eventually washing up on Gemstone Beach. In order to preserve the fossil traces, these stones have often not been completely smoothed in the tumble barrel before being polished, and they often don’t take a high polish.
Two banded ignimbrite stones are also included in these ten from Gemstone Beach (photos below). Banded ignimbrites are volcanic, with distinctive flow bands and small gaseous pockets filled with silica. Ignimbrite originates as the deposit of a pyroclastic flow, which is a hot suspension of particles and gases flowing explosively and rapidly from a volcano. NZ geologist Patrick Marshall originally came up with the term in the 1930s meaning “rain of fiery rock dust”. Some ignimbrite can be very loosely deposited, with lots of pumice in it. If it is buried at depth, it becomes compacted, gases and liquids are squeezed out, and it becomes solid and fine grained and glassy. It has been suggested that this particular banded ignimbrite has been eroded from areas of the approx. 145 million years old Loch Burn geological formation of eastern Fiordland and came down the Waiau River to the coast.
Gemstone Beach has over a kilometre of stones often piled high . Some of these stones may be jasper, stained quartz, colourful quartzite, waxy hydrogrossular garnets, and various breccia and conglomerates (small fragments compressed in a fine matrix). In many instances, for the stones I pick up there, I do not know the exact type of rock from which they originate. Each stone is unique but carries within it a significant part of New Zealand’s geological history. Each stone also tells its own story upon careful reading, and every person can see slightly different messages, landscapes, patterns and depths. These are the “gems” of Gemstone Beach! The five other tumblestones from Gemstone Beach that I sent Sheila are:
To finish with some more photos of Gemstone Beach:
In Part Two of this series of Posts, we look at tumblestones that come from further north, from a little beach just outside of the small town of Kakanui in North Otago.
