I arrived at Seadown Beach near Kakanui in North Otago just before 10am on a cool cloudy morning for a 60 minute fossick. It was two hours before high tide so my usual fossicking area among the rocks at the southern end was under water. There were few stones to be seen on the beach immediately in front of the parking area but I came across some good patches as I walked northwards. I ended up collecting a good range of stones. Twenty-four are featured below.
The most common stone I collect from this beach for tumble polishing is quartzite. One type of quartzite is thought to come from Central Otago (see stone #1 on page 20 of Thornton’s “Gemstones”) and appears in a range of hues from grey to cream to yellow to red. They often contain attractive clouds of mineral colour. Some have tiny clear fragments of quartz, usually apparent only upon close inspection. It is a hard stone and is often nice and smooth already. I came across some very nice specimens. These three are at the grey end of the colour range, with hints of cream and yellow:
A good example of a cream coloured quartzite:
The most common colour is yellow, from a very light creamy yellow to an intense yellow-orange. Here are five from today’s finds:
I found a quartzite containing a mix of greys and yellows:
Red-hued specimens are usually very attractive – though they can often easily be mistaken for jasper:
I have an extended discussion on issues relating to identification in this October 2024 Post, “Quartzites and Jaspers – Identifying Stones: Confronting Confusion”.
There are other types of stones that are also identified as quartzites. I found two this morning. One is black and white, the other has green mineral clouds in it which, if epidote, might mean the stone can be called epidosite:
Another “quartzy” stone with mineral clouds in it:
Some very nice jaspers can be found on Seadown Beach. Three I found this morning, all different in character:
And I think the following stone could also be a jasper, though I have seen suggestions it could something else:
The most spectacular jasper I have found to date anywhere came from Seadown Beach in 2021 – it is #2 in the TumbleStone Hall of Fame.
Another interesting type of stone from this area is fossiliferous limestone. As the name implies, you can often see tiny fossils in them. I picked up a handful, this one being the best specimen:
Sometimes limestone can contain circular features which are fossil rhodoliths, marine nodules of algae. I left this large specimen on the beach:
See also “F is for Fossil Rhodolith in Fossiliferous Limestone”. Fossilierous limestone is a soft stone and to be tumbled with care.
I found a nice beach agate this morning, with interesting patterns on its surface:
Agates can be found along a lot of the nearby North Otago coast, especially All Day Bay a handful of kilometres to the south (see the first two photos in this Otago Rock and Mineral Club site). I find them only now and again on Seadown Beach (e.g., May 2021, March 2022, September 2024, March 2026).
I always keep an eye out for the brown stones that might contain bryozoan fossils. I picked up a couple but I can’t clearly see anything in them:
Finally, what I think is likely to be basalt with feldspar crystals:
I occasionally find such stones (e.g., March 2025) and am fascinated by the size and shapes of the crystals, and sometimes what can been seen in the crystals.
Next stop is the Back Beach at Riverton Aparima.
An Index to all the Posts in this Series is here.
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