A Blog About Stone Gathering, Tumbling and Polishing, and Rocks and Landscapes, from New Zealand – With Musical Interludes (john.tumblestone@gmail.com)
McCracken’s Rest mudstone (argillite), with trace fossils).
I found this stone on the beach at McCracken’s Rest in February 2021 (see Day 11 in this Post). It is an argillite mudstone with trace fossils. McCracken’s Rest is a roadside lookout just under eight kilometres west of Gemstone Beach, Western Southland. Perched on a hill on the edge of a cliff, the lookout provides a stunning view of Te Waewae Bay and the mountains of Eastern Fiordland.
McCracken’s Rest in relation to Gemstone Beach – Google Maps.
McCracken’s Rest – Google Maps streetview.
McCracken’s Rest lookout.
McCracken’s Rest.
Information Display, McCracken’s Rest.
Part of the McCracken’s Rest Information Display.
The beach between Gemstone Beach and McCracken’s Rest (and beyond) lies below cliffs all the way along. Access even at this lookout is not easy. You have to hop over the fence and carefully make your way down a steep slope to the beach below.
Looking west from McCracken’s Rest to the mountains of Eastern Fiordland.
Looking east from McCracken’s Rest along the curve of Te Waewae Bay towards Gemstone Beach, Monkey Island, and Pahia Hill.
Looking up at the McCracken’s Rest lookout from the beach below.
Stones on the beach at McCracken’s Rest – there are sandy patches too.
McCracken’s Rest beach stones.
McCracken’s Rest beach stones.
A sandstone has grains that are visible to the eye while the tiny grains making up a mudstone like this one are not visible without magnification. Argillite is a hardened slightly recrystallised mudstone, sometimes called “metasedimentary”. Along the Te Waewae Bay coast, argillite stones come in grey, green and red, with some banded argillites being brown as well. Examples of these argillite stones can be found here.
The argillite of the Te Waewae Bay coast is a Brook Street Terrane sedimentary rock in which trace fossils are found. A “terrane” is a fragment of the Earth’s crust consisting of a distinct series of geological formations, and it has been transported by plate tectonic processes to its current position. New Zealand consists of a number of such terranes – see pages 34-51 of Peter Ballance’s “New Zealand Geology: An Illustrated Guide” (2017). The Brook Street Terrane runs from Nelson to the south coast of the South Island and has been torn in two by the alpine fault. When lying beneath the ocean surface, sediments of mud were inhabited by small animals which left traces, mostly of burrows and trails, that were preserved in the mudstone. All of this happened more than 250 million years ago, in the Permian Era, offshore from the ancient continent of Gondwana. For more on argillite mudstone and trace fossils along the south coast, see “The Fossilised Worm Cast Stones of Gemstone Beach and Riverton – Part Five: ‘Burrowing Worms’ of the Permian in Brook Street Terrane Rocks East of Tihaka Beach”.
Looking back up at McCracken’s Rest from the beach.
The marks on the stone.
“I made my wayto a hill beside the sea, with salt in the air and sand on my feet… Now I’m far away, these memories still remain”(from “These Memories”, a song by Hollow Coves – see the end of the Post).
McCracken’s Rest is a roadside lookout just under eight kilometres west of Gemstone Beach. Perched on a hill on the edge of a cliff, the lookout provides a stunning view of Te Waewae Bay and the mountains of Western Fiordland (see photo below, far left). I have mixed memories from previous visits here. I made my first fossick in May 2019, when I walked as far westwards as the Te Waewae Lagoon, and found it disappointing, especially compared to Gemstone Beach. I had more productive fossicks in February 2021 (including seeing a large pink thulite – photo below, second from left) and June 2021 (see photo of a find below, second from right). My last visit there, in September 2024, resulted in a large purply-pink thulite find (photo below, far right) but not much else. As noted in these Posts, the beach is largely a continuation of Gemstone Beach, with many of the stone types being similar. However, there is much less diversity here and the stones tend to be more bashed around and less smooth.
A large pink stone – it’s about 15 cms in length. I left it on the beach, far too big for me to tumble polish and too heavy to add to my backpack.
Large thulite stone from McCracken’s Rest.
Today I scrambled down the cliff just before noon on a cool sunny day with a little wind:
McCracken’s Rest.
Looking west at McCracken’s Rest.
Looking east, towards Gemstone Beach, at McCracken’s Rest.
Looking south at McCracken’s Rest.
Looking back up at McCracken’s Rest from the beach.
McCracken’s Rest beach stones.
My McCracken’s Rest finds.
Details of what’s on the Rest’s information panel can be seen in this Post.
I fossicked westwards on the beach for a few hundred metres before returning, spending one and three-quarter hours there. No-one else was on the beach – it is not easily accessible due to the cliff. I came away with 39 finds, some of them very surprising – what is highly likely to be an agate/chalcedony,three poppy jaspers, a dendritic trace fossil stone, and other visually interesting pebbles.
When I first saw this stone, I thought it might be hydrogrossular garnet or quartz. Picking it up, it lacked the waxy feel of a garnet. However, it didn’t quite feel right for quartz – it felt too smooth:
Agate/chalcedony?
The marks on the stone.
Held up to the light.
Back at my accommodation, I examined the stone more closely and noticed a number of semi-circular marks on it. I knew I’ve seen those before but I couldn’t remember where. I was thinking maybe on quartzites. Then I saw a comment by Glenys Stace, in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”, noting that a stone posted by someone had the typical marks of agate/chalcedony. I then remembered where I had seen them before – on agates I have found, such as near Moeraki Village in March 2021 (see towards the end of this Post), on a Birdlings Flat agate I tumble polished in May 2021, and on ones I found on Kakanui’s Seadown Beach in September 2024. In these Posts I say the marks are caused when a stone is slammed into rocks and other stones by waves and/or the current. However, it has been reported by a couple of people I know that the marks are made when a stone has been transported by a glacier. So there is a very good chance this stone is chalcedony – and I have not seen one before along the Te Waewae Bay coast.
The three poppy jaspers I found today – these were unexpected as I have not found these at McCracken’s Rest before:
Tiny orbs in this poppy jasper.
Slightly larger orbs.
The orbs are less well-defined in this poppy jasper.
I also picked up the following small red hematite jasper but it is not a poppy one:
I saw very few trace fossils stones and collected only one – it has a faint trace but, more interestingly, a faint line of dendrites:
Argillite stone with a faint trace fossil and line of dendrites.
The term “dendrite” comes from the Greek word for “tree”, referring to its branching habit. In geology, dendrites are thin, branching crystals, often of some variety of manganese oxide, that grow over a surface in a rock or mineral. They can be found in cracks, as with this stone, or along bedding planes. See “D is for Dendrites”, the second part of this Post. For examples of dendrites in some Ward Beach stones, see the end of this Post. Dendrites are often given as examples of “pseudofossils”, natural objects that may be mistaken for fossils (of a plant leaf, for example).
Four other visually interesting pebbles I collected:
Interesting amygdaloidal stone.
Interesting mix of colours.
“These Memories” by Hollow Coves (2017)
We found our place On the branch of an old gum tree Our feet would sway To a voice in the breeze And birds would sing On the banks of a narrow stream These memories will stay with me
We made our way To a hill beside the sea With salt in the air And sand on our feet We felt the sun As it burnt upon our skin These memories will stay with me
Now I’m far away These memories still remain Now I’m far away You stay with me the same…
Looking east, towards Gemstone Beach, from McCracken’s Rest.
Riverton Aparima’s Back Beach, looking west.
Some stone collecting days are more productive than others. I arrived at Gemstone Beach about 9.30 am, a cool seven degrees but very little wind and the sun was shining. It was about 90 minutes after high tide. The Taunoa Stream was too deep and swift to ford so I was restricted to fossicking on the beach in front of the carpark, a stretch of about 200 metres. I found a dozen or so stones, and gave away a trace fossil stone and hydrogrossular garnet to a man who was picking up stones for his son. This stone is the most interesting of the ones I took away with me.
Gemstone Beach stone.
Other side of Gemstone Beach stone.
After 45 minutes on Gemstone Beach, I decided to drive further west for about eight kilometres to McCracken’s Rest, a roadside lay-by and viewpoint. The Rest is on the same stretch of Te Waewae Bay as Gemstone Beach but the stones tend lack the same quality. There are also bigger stones here.
Gemstone Beach this morning.
McCracken’s Rest.
McCracken’s Rest.
Looking east, towards Gemstone Beach, from McCracken’s Rest.
McCracken’s Rest stones.
McCracken’s Rest stones.
This Post describes my first visit to McCracken’s Rest in 2019. Access down to the beach from the viewpoint is not easy – a fence has to be climbed (avoiding the electric fence part) and a steep slippery slope has to be negotiated. I spent another 45 minutes here and found little of interest until I was about to leave the beach. It was then that I found a large pink thulite stone, 10 cms long. A good candidate for the rock garden.
Large thulite stone from McCracken’s Rest.
Other side of large thulite stone.
Top of stone.
Bottom of stone.
Thulite is the national gemstone of Norway where it was first discovered. As Wikipedia notes, it is manganese that is the source of the pink colour. A thulite stone was January 2022, Stone of the Day #5, and that Post includes a photo of specimens from the Riverton Aparima Museum. Wet thulite stones are often very attractive and often have areas of swirling pink. However, some of them fail to tumble polish well, not taking a shine at all.
On my way back to my accommodation in Riverton, I decided to go on to a third beach, the beach at Howell’s Point, Riverton Rocks, which I know as the Back Beach. I had visited it four days ago and found some poppy jaspers – see “Back to the Back Beach”.
Riverton Aparima’s Back Beach, looking east towards Bluff.
Riverton Aparima’s Back Beach, looking west.
I spent a further 45 minutes fossicking there, but it was largely unproductive. Included in the handful of stones I collected was this trace fossil in argillite.
Trace fossil stone, Back Beach.
Other side of trace fossil stone.
It was a good day to be on the three beaches I visited, and the walking always does me good. But I’m hoping for better results tomorrow when I will head back to Gemstone Beach.
Part 10 reports on a much more productive fossick on Gemstone Beach with Chrissy and Ohla. The first Post in this Series can be found here.
