September 2024 Stone Collecting Trip –Part 15, Fossick at a Slope Point Beach, Friday 20 September

Chrissy and I travelled to Slope Point this morning, a 90 minute drive from my base in Riverton Aparima. Slope Point stones are very different from those to be found on Gemstone Beach, many more of them being of volcanic origin. We visited one of the beaches there for about two and a half hours, leaving just as a heavy downpour of rain hit the region.

Slope Point is the southernmost tip of the South Island, and a handful of its beaches have long been visited by stone fossickers. Recently, landowners have restricted the beaches that can be accessed. Some of the Slope Point stones have arisen from Jurassic Era volcanic activity and debris flows. Petrified wood, fossil tree fern, colourful rhyolites and interesting breccia can be found there. Jocelyn Thornton’s “Gemstones” has an informative page on Slope Point stones (page 35). However, the steep slopes and distance from good roads mean that the fossicker has to be determined and prepared to carry heavy finds some distance back up-hill. Rock and Mineral Club expeditions sometimes head this way. For example, the Southland Geological and Lapidary Club has planned a trip there on Sunday.

When Chrissy and I reached the beach, the tide was low and the sea was very calm. The beach is a small one, maybe only two hundred metres long, with a rock platform at one end and high cliffs with outcrops of conglomerate strata at the other. Today there was a bit more sand on the southern part of the beach than is often the case, but there were still plenty of stones to search through.

Compared to Gemstone Beach, the stones tend to be more knocked around, and many otherwise attractive specimens have chunks out of them, scratches across their surface, or have small holes in them. These pose more of a challenge to the tumble polisher. This morning, spending time looking carefully among the dry stones up the beach proved most productive – for some reason, we found fewer stones of interest at the waves’ edge. I collected about 130 to take home.

I didn’t find any of the sought-after petrified wood, tree fern or chrysanthemum rhyolite this morning (see this Post and this Post for examples). But this first stone is an example of the surprising beauty that can sometimes be found in the Slope Point area:

A Slope Point rhyolite that contains some circular features that can sometimes be found here:

A very dark stone, with some circular features, which I think is also a rhyolite:

Probably a volcanic breccia:

This stone is probably rhyolite but it seems to have some tiny angular fragments in it too:

Sometimes it can be difficult to decide whether the features in a stone are crystals or fragments of other stones, as in this small pebble:

A similar shaped pebble:

Two lighter-coloured stones, also with intriguing tiny markings:

Three more of the lighter-coloured finds from this morning:

And six of the darker-coloured finds:

The cliffs along the north of this beach consists of a strata of conglomerate rock. There are lots of rounded stones embedded there, many of them larger than a fist. It is also possible to find conglomerate stones on the beach, made up of small rounded fragments, like this one, which also has an interesting “other” side:

I try to collect reasonably smooth stones – the chance of a successful tumble polish is enhanced by this. However, despite its chunky character (hollows and jagged ridges), I couldn’t leave this one behind. I will need to use more coarse grit in the tumbler than usual for it.

I was very surprised to find a nice specimen of yellow quartzite. It is much more common along the North Otago and Canterbury coastline:

On the way back home, I stopped briefly to take a look at a new Information Kiosk at the Slope Point tourist carpark – it has great information on the history of the area. But the wind and rain made it unpleasant to linger. It looked like a toilet block is also being built there.

The next Post in this Series features another fossick on Gemstone Beach, highlighting some colourful finds. The Index to the Posts in this Series can be found here.