Rough Stones – TumbleStone

Index to June-July 2022 Fossicking Trip

For four weeks in June-July 2022, I travelled by car from my home in Whanganui to the south of the South Island. Along the way, and when I got there, and during my return, I visited a number of beaches, fossicking for stones to take home to tumble polish. Each day I also wrote a Post about that day’s fossicking. This Index allows you to click on a link to be taken to the relevant Post. The photos above each link give you an idea of the beach and stones in the Post.

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1) Ward Beach Wednesday 22 June

2) Birdlings Flat Thursday 23 June

3) Timaru South Thursday 23 June

4) Seadown Beach, Kakanui Friday 24 June

5) Seadown Beach, Kakanui Saturday 25 June

6) Gemstone Beach Monday 27 June

7) Back Beach, Riverton Aparima Tuesday 28 June

8) Gemstone Beach Wednesday 29 June

9) Back Beach, Riverton Aparima Thursday 30 June

10) Gemstone Beach Thursday 30 June

11) Gemstone Beach Saturday 2 July

12) Gemstone Beach Sunday 3 July

13) Gemstone Beach Monday 4 July

14) Gemstone Beach Tuesday 5 July

15) Gemstone Beach Wednesday 6 July

16) Slope Point Thursday 7 July

Kakanui’s Seadown Beach.

17) Seadown Beach, Kakanui Sunday 10 July

It has been suggested that this stone is argillite (silicified mudstone), with two different types of mud in it.

18) Seadown Beach, Kakanui Monday 11 July

Flint at the top of this stone.

19) Ward Beach Wednesday 13 July

Diane’s Stone, and an Introduction to Jasper

Diane’s jasper stone after 220 tumble

Piece of Coromandel Peninsula jasper given to me by Jack Geerlings,

Jasper rock outside Riverton Museum Te Hikoi.

Jasper stone on the beach near McCracken’s Rest, an extension of Gemstone Beach.

Just under a year ago, my niece Diane bought a new house in Christchurch. While doing work in the garden, she found a stone that she thought was potentially interesting. She showed it to me when I was visiting her and I recognised it as jasper. The stone was in a rough condition. It was far from smooth, and running through the middle was a brittle and pitted silica band. The photos below are of the stone after it was washed and allowed to dry:

Diane’s jasper stone

Detail of Diane’s jasper stone

Diane’s jasper stone

I thought that tumbling it would at least bring out the colour, so I offered to take it away to work on it.

What is jasper? Jasper is a well-known red stone found on many beaches in New Zealand, especially in the South Island. I have found it on beaches like Birdlings Flat in Canterbury, and at Riverton and Gemstone Beach in Southland. It tends to stand out amongst other stones because of its deep red colour:

Jasper stones found on Birdlings Flat (wet)

Jasper stones found on Birdlings Flat (dry)

Jasper stone found on Birdlings Flat

Jasper stone on the beach near McCracken’s Rest, an extension of Gemstone Beach.

I once found a rock in a track on the farm I grew up on, The Mains near Waikaka. When trying to identify it, I thought first of all that it was chert but it turned out to be jasper (Minerals.net states that “when Jasper is dull and lacking interesting colors or patterns, it is not Jasper but rather Chert”). I eventually broke it up, with difficulty – to put it technically, jasper “fractures conchoidally” (like flint – Geology.com points out that jasper, chert and flint are very similar, all being varieties of opaque microcrystalline quartz). When polished, the pieces of the rock I found had a very glossy, almost waxy, quality.

The farm track on “The Mains” where I found the jasper rock.

The jasper rock in the farm track.

Jasper rock found on The Mains.

It was very difficult to break up the jasper rock.

The pieces were very sharp and angular.

Some of the pieces broken from the jasper rock.

The pieces of jasper after tumbling.

Polished pieces of the jasper rock.

I later discovered that jasper is very common around the Waikaka area, being part of the gold-bearing quartz gravels of the area – see the Tumblestone Posts “Jasper Stones and Petrified Wood, Shepherd’s Creek, Waikaka” and “Waikaka’s Auriferous (Gold-Containing) Quartz Gravels“.

In Riverton, outside the museum Te Hikoi, a number of rocks from Southland are on display. One of them is a large piece of rounded jasper. Inside the museum, a number of smaller jasper stones are displayed, including a dark green one.

Jasper – Detail of information panel outside Riverton Museum Te Hikoi.

Information panel outside Riverton Museum Te Hikoi.

Jasper rock outside Riverton Museum Te Hikoi.

Some of the rocks on display outside Riverton Museum Te Hikoi. Source: https://www.tripadvisor.co.nz/LocationPhotoDirectLink-g670372-d6982462-i110952775-Te_Hikoi_Museum_and_Information_Centre-Riverton_Southland_Region_South_I.html

Jasper display in drawer inside Riverton Museum Te Hikoi.

When I recently visited Jack Geerlings in Winton, who has an extensive collection of stones and rocks from southern New Zealand, I noticed he had a number of pieces of jasper (see photos below). He had collected some from the Coromandel Peninsula, in the North Island, and generously gave me a piece. Outside his shed, where he had a number of rocks and boulders on display, a rock of red and green jasper can be seen. And inside his shed, he showed me a polished stone of orbicular jasper. In her book “Collecting Rocks, Gems and Minerals” (3rd edition, 2016), Patti Polk has an extensive section on different types of jasper. On pages 121 and 122, in her entry on orbicular jasper, she states: “Orbicular jasper is generally a type of highly silicified rhyolite or tuff that has quartz and feldspar crystallized into radical aggregates of needle-like crystals that form orbicular or spherical structures.” The photos below include page 122 from her book, illustrating some of the variants of orbicular jasper.

Piece of Coromandel Peninsula jasper given to me by Jack Geerlings,

Red and green jasper rock outside Jack Geerlings’ shed.

Orbicular jasper from the collection of Jack Geerlings.

Examples of orbicular jasper. Page 122 of Patti Polk (2016) “Collecting Rocks, Gems and Minerals”

To find out more about jasper, I consulted one of my books, “The Illustrated Guide to Rocks and Minerals” (2015) by John Farndon. On page 204, he notes that jasper is a red, green or yellow variety of chalcedony. Chalcedony arises when quartz crystals forms at low temperatures in volcanic cavities. The crystals can be so small that they are visible only when magnified, which is the meaning of the term “cryptocrystalline”. The general name for cryptocrystalline quartz (also called “microcrystalline”) is chalcedony, which comes in a vast array of colours and patterns. As Farndon notes, it includes blood-red carnelian, wine-red jasper, brown-banded agate, green-moss agate, apple-green chrysoprase, and black and white onyx. The colour depends on what minerals seep into the rock. The presence of iron causes the red colour in jasper. In fact, jasper is often referred to as a coloured form of opaque agate, agate being one of the major types of chalcedony (see, for example, the wikipedia entry on chalcedony).

Page 204 of John Farndon (2015) “The Illustrated Guide to Rocks & Minerals”

Page 205 of John Farndon (2015) “The Illustrated Guide to Rocks & Minerals”

Page 229 of Ronald Bonewitz (2008) “Rock and Gem”

Mindat.org has a lot of photos of different variations of jasper. Below are also photos of some different types of jasper, with the one on the right showing rough and tumbled stones.

Varieties of jasper. Source: https://i.pinimg.com/originals/ea/bd/02/eabd02a66df8678390f116849b97d0a9.jpg

Some varieties of jasper. Source: https://astrokapoor.com/types-jasper-properties/

Jasper, rough and polished. Source: https://www.pinterest.nz/pin/760263980824785155/

To get back to Diane’s jasper stone: After tumbling for just over a week (9 days and 19 hours, to be precise) in 220 silicon carbide grit (along with other stones), followed by five and a half hours tumbling in water and sunlight soap, the stone’s colours emerged much more clearly. Nevertheless, it was still rough in places, with the middle band of silica especially pitted:

Diane’s jasper stone after 220 tumble

Detail of Diane’s jasper stone after 220 tumble

Diane’s jasper stone after 220 tumble

However, the stone showed promise. I next tumbled it in 320 silicon carbide grit for another week (seven days and one hour to be exact), followed by 21 hours in sunlight soap. There was a small improvement in the surface condition of the stone, though of course the pits in the middle silica band were too deep to erode away:

Diane’s jasper stone after 320 tumble

Detail of Diane’s jasper stone after 320 tumble

Diane’s jasper stone after 320 tumble

Detail of Diane’s jasper stone after 320 tumble

I next tumbled the stone in pre-polish tin oxide for five days, followed by a 21 hour soap tumble. Then it spent nearly 12 days in pro-polish tin oxide, finally spending just over four days in a borax burnishing tumble. Unfortunately, these stages seemed to bring out various lines of weakness in the stone, and it failed to take a polish. I didn’t think that further tumbling would improve it:

Diane’s jasper stone after polishing

Detail of Diane’s jasper stone after polishing

Diane’s jasper stone after polishing

Detail of Diane’s jasper stone after polishing

Diane’s jasper stone after polishing

While I found this disappointing, it is not unusual for some jasper. Many of the jasper stones found on the beach have a chip out of them or some kind of crack. There is often a brittleness in jasper that gives rise to this.

At least Diane now has a much cleaner and more colourful stone.

Gemstone Beach Gems Off to Germany

I mentioned towards the end of a previous post that I had met Maike and Martin, a young couple from Germany, on Gemstone Beach in March. I agreed to tumble-polish some stones for them. Today I finished the process, and Petra my wife will take the stones to Germany when she travels there in a couple of days.

Altogether, Maike and Martin collected 83 stones on Gemstone Beach. The largest is 6 cms by 3 cms, the smallest being about half the size of my small finger-nail. All 83 fitted nicely into a 3lb tumbling barrel. I am very impressed with the resulting product, an excellent set of polished Gemstone Beach “gems”! Maike and Martin collected well.

The following are photos of the original stones, dry, then how they looked after their first tumble in 320 grit, and then how they looked after their final polish:

The 83 stones as found on the beach.

After the first tumble in 320 grit.

After the final polish.

Firstly, the stones were tumbled in 320 grade silicon carbide for seven days, then tumbled in Sunlight soap for six hours. Secondly, they were in a five-micron tin oxide “pre-polish” tumble for five days, then tumbled in Sunlight soap for 16 hours. Thirdly, a one-micron tin-oxide “pro-polish” stage took eight days, followed by 27 hours in borax soap. The whole process took 22 days. This is probably the shortest time I have ever polished stones, but the outcome was very good. Initially the stones weighed 780 grams, finishing up at 689 grams, thus losing 10% of their mass, most of it in the 320 tumble stage.

The following photographs provide comparisons of some of the polished stones with how they looked initially, when found on Gemstone Beach. To start off with, here are three of the larger ones:

Maybe a kind of argillite, a mudstone.

Banded rhyolite stone.

Further comparisons for larger stones:

As found on the beach.

Polished.

Different textures.

As found on the beach.

Polished.

Some of the medium-sized stones:

Two polished stones.

Before polishing.

Polished.

As found on the beach.

Polished.

Smaller stones:

White quartz stones as they were on the beach – practically polished already!

Some other small stones from the beach.

Some small green stones from the beach.

The polished stones.

One of the stones is a small jasper button:

Before polishing.

The polished jasper stone is at the right.

Finally, some of the smallest stones collected by Maike and Martin:

Before polishing.

After polishing.

When packaging the stones to send to Germany, to complete Maike and Martin’s set of outstanding Gemstone Beach stones, I added a hydrogrossular garnet and a stone with a fossil worm cast. These are iconic Gemstone Beach gems, with the hydrogrossular garnet especially sought after, and the fossil worm cast being reasonably distinctive to this coast. As they were absent from Maike and Martin’s haul, I took the liberty of adding them to the package heading overseas.

015 — White hydrogrossular garnet (left) and what is probably an argillite stone with a fossil worm cast (right).

South Island Stone Collecting Trip, Part Two – Riverton to Kaikoura

Continued from Part One.

Next stop was Riverton at the very bottom of the South Island, where we were based for the next three weeks – many thanks to Helen and Ray for the generous use of their holiday home. We collected many beach stones from the Riverton area and from nearby Gemstone Beach at Orepuki. The weather was cool and windy at times but not bad enough to discourage stone collecting. We met a handful of fellow stone collectors at Gemstone Beach and exchanged greetings and stories. We also spotted dolphins swimming off the beaches at Riverton.

Riverton’s Back Beach, a great source of stones to polish

Fossicking for stones, Back Beach, Riverton

Crashing waves, Back Beach, Riverton

Hector’s dolphins, Riverton

Along the coast from the Back Beach, Colac Bay hill in the background

A stormy day, Riverton coast

Gemstone Beach, near Orepuki

There were many stones exposed on Gemstone Beach

While based at Riverton, we took a day trip eastwards to Waipapa Point, Slope Point and Curio Bay, the latter being well known for its petrified forest that is uncovered at each low tide.

Waipapa Point lighthouse

Sea lion emerging from the surf at Waipapa Point

Waipapa Point

Slope Point is the southernmost part of the South Island

Rough seas at Slope Point

The stairs down to Curio Bay

Petrified fallen three at Curio Point becomes apparent as the tide recedes

Petrified tree stumps at Curio Bay

Petrified wood in the rocks at Curio Bay

Petrified tree stump, Curio Bay

One day we walked the Long Hilly Track through an old gold mining area near Orepuki. This included part of the 40 kilometre long Port’s water race, built in the 1870s and 1880s with the help of Chinese miners. We visited the Riverton Museum and found an excellent display on the Chinese goldminers. On a visit to the Southland Museum in Invercargill, we saw a natural history room that included a lot of local geological displays and information.

Round Hilly Track information panel.

Most of the track is through bush like this. It was a cold wet day.

About Port’s water race – 40 kms long

Port’s water race runs alongside the track for hundreds of metres

Ray starting at the bottom of part of Port’s water race

At times Port’s water race runs through short tunnels

Dams were constructed to feed water races for the gold mining.

An area behind one of the dams.

Information panel on the Chinese gold miners

A substantial Chinese settlement is now only bush

The southern-most Chinese settlement in the world

On the trip north, on the way home, we stopped off to see the Moeraki Boulders in North Otago. Some sea mist came down even though it was the middle of the day. The boulders are large spherical rocks, concretions that have been exposed through shoreline erosion from coastal cliffs. They consist of mud, fine silt and clay, cemented by calcite. The degree of cementation varies from being relatively weak in the interior of a boulder to quite hard at its outside rim. The boulders are cracked and eventually fall apart after having been exposed for some time.

Tourists in the midday sea mist at the Moeraki Boulders

The Moeraki Boulders are a popular tourist attraction

Moeraki boulders on a misty midday

Moeraki boulders

The boulders originate in thecliffs behind the beach

The boulders eventually collapse

A day was spent at Birdlings Flat, near Christchurch, where we collected quite a few stones for polishing. We walked to the point where the stony beach meets the volcanic mass of Banks Peninsula, briefly disturbing a resting seal. The tide was low enough for us to look at the stones in the small bay past the seal.

Birdlings Flat stones, among the best to polish

The seal that I stumbled upon

Going as far as possible at the Banks Peninsula end of Birdlings Flat

We also took the opportunity to visit Akaroa on Banks Peninsula where we saw thick clouds rolling slowly down over the hills.

Clouding rolling down the hills at Akaroa

Akaroa clouds

The road further up the east coast of the South Island, through Kaikoura, was open – it had to be rebuilt after the November 2016 magnitude 7.8 earthquake as well as additional landslides caused by recent storms. So we were able to view the earthquake aftermath, including the land that been raised out of the sea. Some parts of the coast were uplifted by six metres. One of the places we visited on the Kaikoura peninsula was Point Kean, well-known for its seal colony. A large area of many hectares/acres now lies dry where it once was under the sea.

Large uplifted area, formerly under the sea, at Point Kean, Kaikoura

Point Kean, Kaikoura, land uplifted out of the sea by 2016 earthquake

Pont Kean, Kaikoura, looking back to the parking area

Seals are very relaxed about the people walking around at Point Kean, Kaikoura

Lounging seal, Point Kean, Kaikoura

Rain water pool on rocks previously under the sea

The sea looks a long way away

Off Point Kean, Kaikoura

Some interesting folded rocks have been exposed by the earthquake

Newly exposed folded rocks, Point Kean, Kaikoura

Then it was home across Cook Strait, a choppy but not uncomfortable crossing.

Leaving the South Island on a Cook Strait ferry

Passing another ferry in the middle of Cook Strait

South Island Stone Collecting Trip, Part One – Oparara Basin to Lake Tekapo

I have recently returned from a few weeks in the South Island of New Zealand, travelling by car, collecting stones from places like Charleston, Riverton, Orepuki and Birdlings Flat and visiting interesting landscapes like the limestone caves and arches of the Oparara Basin (north of Karamea), Arthurs Pass, Lakes Pukaki and Tekapo, Curio Bay, Waipapa Point, the Moeraki boulders, and the post-earthquake Kaikoura coast.

One of the first places we stayed at was Karamea in the north Buller region of the West Coast. From there we drove the narrow gravel road north to the Oparara Basin and walked to the Oparara Arch, Moria Gate and other limestone caves and landforms.

Oparara Arch, towering high up, a limestone feature

The cave beneath Oparara Arch

In the Oparara River, just below the Oparara Arch

Moria Gate, another limestone arch/cave

Looking out of the cave onto the river at Moria Gate

Looking upstream at Moria Gate

Moria Gate limestone, in the cave

Inside the “Crazy Paving Cave”, Oparara Basin – the patterns are made by dried mud

A rare protected native spelungula spider on the wall of the “Box Canyon Cave”, Oparara Basin

We saw a lot of wekas in the Buller/West Coast area – a cheeky native flightless bird. This one was in the Oparara Basin carpark.

I collected a small number of limestone stones from the Oparara River – they appear to have fossilised shells in them.

Going south along the West Coast, beyond Westport is the town of Charleston and its small twin bays, Constant Bay and Joyce Bay. Constant Bay was named after the ketch “Constant” whose Captain, Charles Bonner, in the mid 1860s managed to squeeze the boat into into the tiny bay, bringing supplies for the town that had sprung up due to the discovery of gold. The rocks that line the shore of these bays have large veins of quartz with masses of mica in them. At the northern end of Joyce Bay we came across of pocket of stones and rocks from a vein that must have been almost pure mica. We chose one small boulder-sized rock to bring home.

Constant Bay

Veins of mica-rich quartz in rocks at Constant Bay

Another detail of Joyce Bay mica rock

Masses of mica in rock at Joyce Bay

Mica in quartz vein, Constant Bay

Rock brought home from Joyce Bay. It must be at least 95% mica. Large mica piece at bottom centre, other pieces of mica throughout the rock

Detail of Joyce Bay rock made up primarily of mica

There is so much mica in the rocks around Constant and Joyce Bays that the sea sparkles with it.

One hundred kilometres south of Charleston is Kumara, where we undertook a short walk to see Londonderry Rock. This enormous 4000 tonne glacial erratic was dislodged by miners while sluicing for gold in the early 1880s. As noted on the information panel at the start of the walk, local legend has it that when it was dislodged from its position it caused earthquake-like shudders that stopped the clock in the post office!

Information Panel at start of the short walk, near Kumara

4,000 tonnes Londonderry Rock; Petra standing to the right side

Londonderry Rock, towering and massive

Along the track are many large boulders left over from the gold sluicing

Hidden in the bush, large piles of boulder tailings

The clock stopped!

Driving across Arthur’s Pass, we passed Castle Hill, Omarama and Lakes Pukaki and Tekapo.

Castle Hill limestone outcrops

The clay cliffs near Omarama

Omarama’s merino sheep statue

Aoraki/Mt Cook, New Zealand’s highest point

Lake Tekapo

Lake Teakapo, with Aoraki/Mt Cook in the distant clouds

Continued in Part Two.

Jasper Stones and Petrified Wood, Shepherd’s Creek, Waikaka

Alluvial quartz gravel along Shepherd’s Creek, near Waikaka School – looking north from the bridge

On the road alongside Shepherd’s Creek, Waikaka

A number of the jasper stones collected near the Waikaka School

Petrified wood found at the Shepherd’s Creek, Waikaka

In the last week of July 2017, on a visit to Southland, I decided to take a look at what stones I could find along a small stream near the Waikaka Primary School, the school I had attended when I was a boy. This stream called Shepherd’s Creek, enters the Waikaka River about 4 kms (2.5 miles) further south, on the farm I grew up on, “The Mains”.

Below is a map of the location of Shepherd’s Creek near Waikaka School (Google Maps, satellite view) – The Creek is in blue, the area where I looked for stones in July 2017 is outlined in black:

S Creek School aa

Below shows where Shepherd’s Creek (blue) joins the Waikaka River (purple), on “The Mains”, the Paterson family farm where I grew up (the northern boundary of the farm is outlined in the black dashed line):

S Creek Mains lge yy

My sister Helen accompanied me in the trip from Gore to Waikaka. We parked not far from the old railway houses, outside the school, just down from two small grazing ponies, and walked down to the creek. There were trees here when we were children but they have recently been removed, pasture now running right up to the banks of the creek. The stream has a bed of stones. And along the stream sides, especially on the bends, there are areas of deposited stones.

Helen on the bridge over Shepherd’s Creek, Waikaka

Looking south from about 100 metres upstream from the bridge.

Helen fossicking for stones

Stones on the streambed.

GRavel along the stream banks.

Stones are often deposited on the inside of the stream bends.

The predominant stone is white quartz, sometimes stained brown, with a sprinkling of other types including quartzite. Surprisingly, we found a number of pieces of red jasper of varying shades, including some large rocks.

Jasper stones collected at Shepherd’s Creek, Waikaka, near the School

Large piece of red jasper, Shepherd’s Creek, Waikaka

The largest jasper rock we found at Shepherd’s Creek

This large piece of jasper now resides in my sister Helen’s garden in Gore

The following are a number of the stones after being polished in 220 grit, the second stage of the five stage process of tumble polishing.

A selection of individual jasper stones:

Three of the other stones collected:

Probably a quartzite stone

A stone stained brown by tanins in the creek – see next photo

The stained stone after tumbling for a week in 220 grit – it looks like agate

I also came across, quite unexpectedly, a piece of petrified wood, and I also picked up another small whitish stone that could be some kind of petrified wood.

Petrified wood, found at Shepherd’s Creek, Waikaka

Petrified wood found at the Shepherd’s Creek, Waikaka

This stone could also be petrified wood, but can’t be sure

Other side of possible petrified wood, Waikaka

The two poles holding up the School sign are in old dredge buckets, remnants from a period at the start of the twentieth century when the area around Waikaka was busy with a number of gold dredges.

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Since this trip, I have done some research into the history of gold mining at Waikaka. Later posts in this Blog will outline this history and the role of gold dredging around Waikaka and on “The Mains”.

Slapton Sands, Part One: A Visit, Mid-2016

In mid-2016 a visit was made to some beaches on the south coast of England. One of these beaches was Slapton Sands, about 45 kms east of Plymouth. Driving through the village of Slapton, you come out to the coast just north of Slapton Ley, the largest natural freshwater lake in south-west England, being 2.4 kms (1.5 miles) long. The Ley is separated from the ocean by a bar of shingle, known as the Slapton Line, with Slapton Sands being the 4.8 kms (3 miles) long shingle beach on the ocean side.

The pebble beach at Slapton Sands, near the village of Slapton

On the Slapton Sands pebble bar

Slapton Sands pebbles

The gentle waves on a still afternoon, Slapton Sands

Slapton Sands pebbles

Below are two views northwards of Slapton Sands from the village of Torcross, just a couple of kilometres south of where the above photos were taken. The first photo was taken in 2012 and is from the Flickr account of Mark Coleman, with the second photo being from the “Essentially England” website page on Slapton Sands:

A two minute YouTube clip of Slapton Ley, Slapton Sands and its local region, mainly from an aerial drone, produced by the Field Studies Council. It includes views of the Field Studies Council’s Slapton Ley field centre, the Start Bay field centre, and Slapton Ley Nature Reserve.

A two minute YouTube clip posted in 2016 by Cornwall and Devon TV, on Slapton Sands for tourists – very beautiful.

A six minute YouTube clip of a person’s visit to Slapton Sands in 2011, showing Slapton Ley and its birdlife, the beach, and surrounding features.

The history of the Slapton Ley and Sands area is presented on the website of the Slapton Line Partnership, going back 100,000 years – click on the small circles under the timeline.

Another Visit to Birdlings Flat, Late June 2016 – Part Three: Seven Types of Stones Collected

During the six to seven hours spent at Birdlings Flat and nearby beaches during two and a half days at the end of June, I collected just over eight kilograms of stones. These consisted of a number of different types of stones. After my two previous visits, I had a good idea of what I was looking for, based on the results of some tumble polishing as well as my own preferences. There are many greywacke stones on the beach, the common grey beach stones of New Zealand, as well as a wide range of other types.

Following are listed the seven types of stones I collected during this visit:

Yellow-patterned Quartzite; Red Jasper; Agates; Green (Quartzite?); Patterned; White Quartz and Other Light-Coloured; Others.

Yellow-patterned Quartzite – This can easily be found at Birdlings Flat and is perhaps my favourite stone from there. I discovered a small boulder of it, that filled both my hands – which I had to leave at the beach. I have brought home at least two hand-sized specimens. There are a number of subtle colour variations of this stone, the best seeming to be a clear to light coloured quartzite with curtains or swirls of “gold foil” throughout it. The intensity of the gold/yellow can vary from stone to stone as can the patterns inside it. During this trip, I sought to collect stones exhibiting these variations.

Dry stones, as collected in late June

The same stones, wet

An idea of size

Collected earlier, smaller and with brighter yellow through it

Collected earlier

Collected previously from Birdlings Flat – swirls of gold through the clear silica

Collected earlier

Red Jasper – Red jasper stones can often be found on South Island beaches. They are reasonably easy to find at Birdlings Flat, where they can be of good size and quality. Many jasper stones have silica veins, sometimes bright red veins as well, and some other mineral staining can be present. They can be brittle, with chips and pits, making them difficult to smooth and polish.

Dry stones, probably jasper, collected from Birdlings Flat in late June

The same stones, wet

Collected at Birdlings Flat at an earlier date

Collected earlier

Agates – Birdlings Flat is well-known for its agates. A wide range of sizes, shapes and types can be found. It took me a while before I learned to spot them. The best way is to look towards the sun and your eye will be drawn to the light shining through them, even amidst a whole mass of other types of stones. On this trip, I found my largest agate so far, and a very small one with a green staining.

The agates collected at Birdlings Flat, late June, in their dry state

The same agates, wet

A sense of their size

Anagate collected at Birdlings Flat at an earlier date

Moss agate, from Birdlings Flat, collected earlier

Coloured agate, Birdlings Flat, collected earlier

Green (Quartzite?) – One of the interesting types of stones to be found at Birdlings Flat is green and I suspect is a type of quartzite. Again, there is a great diversity of them, from pale green through to lime green through to darker greens. I find them quite attractive and relatively easy to spot.

Dry green stones

The same green stones, wet

Patterned – I find myself drawn to even greywacke stones and other grey (or common coloured) stones if they have veins of white quartz through them or if they display layer patterns.

Dry

Wet

White Quartz and Other Light-Coloured – Going through the stones I collected, I find there are a number of white quartz stones and other white or light-coloured stones. These tend to catch my eye on any beach, standing out from the sand or the predominant grey of the most common stones on South Island beaches. I have learned to be more restrained in my collection of white quartz as it is easy to spot it and can soon mount up in the collection bag.

Dry

Wet

Others – What’s left in my collection bag after the rest have been taken away:

Pink stones are rare but present at Birdlings Flat. Some of these stones include ones of volcanic origin, characterised by small white pits

The same stones, wet

Dry, and…

…wet

Pre- and Post-100 Grit

When collected from a Riverton beach, stones are already rounded and smooth from hundreds of years of natural tumbling. When wet, the stones reveal their polishing potential – polishing brings out the colours more intensely and fixes their shine.

Below are photos of Riverton stones before going into the barrel with 100 size silicon carbide grit, the first stage of tumbling, and after four days in the of tumbling (they then go back for another three or four days to complete the first stage of the smoothing process):