New Zealand beaches lend themselves to stone collecting. Most beaches have free access, and stones are easy to find.
I use and old tumber with large barrels. Usually I will put a large amount of course silicone carbide grit in my tumbler and let is run out over 4 weeks. If the stones are really rough, I will repeat this process. To keep track of this I keep a piece of masking tape stuck on the lid with a note saying what is in the barrel, and what stage the grinding is up to.
After that, I give the stones 2 weeks in fine grit. Then, 1 week in water with several scoops of washing machine soap powder added. This really cleans the stones up,cleans up the barrel, and gives the stones a very good prepolish. Then, after giving everything a thorough wash, I use tin oxide in the same barrel to produce the final excellent polish.
Some tumbled stones in my collection:
Orepuke Beach in Southland is well known for Grossular Garnet, and many other coloured stones. This beach is becoming known as Gemstone Beach.
Slope Point is the southern most tip of the South Island. On these beaches can be found very colourful and patterned rhyolites, or Flower Stones. My favourite ones are those with orbicular patterns.
Plasma Chert – limonite and prase, is collected on the beaches south of Oamaru.
Seam agate is often found on the beaches from Hamden south to the Moeraki Peninsula. Many of the agates show colourful plumes and black goethite inclusions. Small lace agates – chalcedony with a white outer coating can be found on the south side of Moeraki Peninsula.
Birdlings Flat on the way to Akaroa is a favourite collecting place for agates, petrified wood and other colourful stones. If you go there, be sure to call into the Gemstone and Fossil Museum run by Vince and Colleen Burke.
Some very inteesting black and white agates can be picked up on a small land slip on Mt Somers Station, Canterbury. The stones are small and sometimes hard to destinguish from the results of what sheep leave when wandering through the area. First discovered by Alan Wells, a long-time Canterbury rock collector, the agates are called Alans Slip Agates. Some are even hollow, and filled with water, which eventually dries out.
The Canterbury Mineral and Lapidary Club have been allowed to dig for agates at Whitecliffs in inland Canterbury. Some of the small material lying around on the surface tumbles up well. There is a mixture of porcelain and sardonyx agates with many other colours.