A Blog About Stone Gathering, Tumbling and Polishing, and Rocks and Landscapes, from New Zealand – With Musical Interludes (john.tumblestone@gmail.com)
In Te Ara, the online New Zealand Encyclopedia, is a map of beaches in New Zealand where you can find agates and other interesting stones. This is a very selective map and does not include, for example, Riverton at the bottom of the South Island, one of the best places for semi-precious stones.
“Although New Zealand lacks the commonly accepted ‘precious gems’ (diamond, ruby, sapphire, emerald), many local stones deserve our recognition” (from the Introduction to “Gemstones”).
This booklet, originally published in 1985 in the Mobil New Zealand Nature Series, is long out-of-print but now available online as a pdf file. The pdf file is 36 pages long (each of its pages consist of two of the original booklet pages when its comes to numbering – the original booklet numbered each side of each sheet, making 74 pages). It is a great source of information on the range of precious and semi-precious gemstones to be found in New Zealand – from greenstone to agate to jasper to petrified wood, and many more. It contains some great photos of the many different types of stones, supplemented with notes on where these specimens have been found (see below for the entry on “Carnelian”). Reference is often made to places such as Birdlings Flat, Rangitata River, Orepuki, Kakanui, Mt Somers, the Coromandel Peninsula, and Takaka.
Joyce Thornton also wrote the entry on “Gemstones” for Te Ara, the Online NZ Encyclopedia. This entry has some excellent photos of different types of stones, such as “Silicified Wood and Plant Material“. “Chert, Flint and Jasper“, and “Greywacke Pebbles with Quartz Veins“. In 2004, she received the NZ Order of Merit for services to Earth Sciences.
This is the second significant New Zealand book published on rock tumbling (after the Coopers’ book), though its scope is broader, “rockhounding” in New Zealand in general. I ordered this book through Amazon and they sourced it from Bookhaven, a second hand bookstore in Wellington.
“The New Zealand Rockhound” by Natalie Fernandez was published in 1981 by Boughtwood Printing and Publishing House, Auckland. The book measures 14 cm by 21.5 cm and has 191 pages. Beach stones, my prime interest, are only one form of rocks – they are very useful for stone polishers because they are already relatively smooth and rounded, already the subject of hundreds of years of “tumble polishing” in rivers and ocean. Rockhounds need to be able to identify rough and dirty rocks in the field – all I have to do is wet a beach stone and decide if I like the result.
“The New Zealand Rockhound” covers rockhounding in New Zealand in general. Chapter Six, “The art of the lapidary”, starts off with five pages on rock tumbling before going on to discuss cutting and grinding and other means of working with rocks and stones. Chapter Four on “Rocks and minerals” provides an introduction to the topic in the context of New Zealand’s geology, and Chapter Five, “Locations”, provides an annotated list of NZ places to find interesting rocks.
Fernandez’s book also has a delightful frontispiece of stamps with rocks and fossils on them:
On the way home from our South Island holiday, once the seed had been planted that we would start polishing stones, in Wellington I visited three second hand bookstores in search of books on rocks and rock tumbling. I found this book at that time, probably the first New Zealand book on rock tumbling.
“New Zealand Gemstones” by Lyn and Ray Cooper was published in 1966 by A.H. and A.W. Reed, Wellington. It is a hardback book, 22 cms by 14 cms, 125 pages long and cost me $20 at ArtyBees secondhand bookstore.
The key chapter for me at this early stage was Chapter Three, “How to tumble-polish”. It is now a bit out-dated in parts, as new technology has since changed some aspects of rock tumbling, but it provided me with the basic ideas about what tumble polishing involves and what its key principles are.
Chapter Two was the next most interesting, “Where to find the stones”, the location of interesting stones in New Zealand based on the authors’ own expeditions to different places. Again, some of this information is now out-dated and is at least partly constrained by the authors’ experiences (there are some parts of the country they have not been to), but provides an invaluable starting point. (Their comments led me to take a trip to the Coromandel Peninisula beaches not long afterwards.) Chapter Six, “What to do with stones”, was on a topic that I realised I would need to pay some attention to sooner or later.
A batch of stones mid-way in the tumbling-polishing process
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):
An internet search for rock tumblers took me to the website of Rotorua Lapidary who advertised that they sold rock tumblers. So I drove over there one day and bought three machines – two Lortone Model 33B Tumblers (each of which has two 3-pound rubber barrels) and one Lortone Model 45C Tumbler (which has a 4-pound barrel).
I had to guess what might turn out to be appropriate for us – I thought that Petra and I could each keep one of the 33B tumblers busy, and there is the flexibility of the two barrels – and we could share the larger one. Each 3-pound barrel is about 10 cms deep and 10 cms in diameter. The 4-pound barrel is 9 cms deep and 15 cms in diameter. The “pounds” refer to the weight of the load of stones that can be placed in them – three pounds is 1.33 kgs and four pounds is 1.8 kgs.
Colin Simmons of Rotorua Lapidary told me that he started rock tumbling in 1966. He opened his shop in Rotorua in 1981 and runs it with his wife Bev. He happily spent a long time with me, answering my questions about rock tumbling and offering advice based on his extensive experience. I am very grateful for the help he provided. Along with the tumblers I bought three grades of silicon carbide grit (100, 220 and 320), tin oxide polish powder (two grades – the “pre-polish” and the “pro-polish”), and plastic pellets (which are used to cushion the tumbling stones once they get more rounded or to make up a load if there’s not enough stones for the barrel). I was now ready to set up a small stone tumbling operation!
Beach stones are great for the tumble polisher. Compared to stones found in the ground, and in streams and rivers, beach stones tend to be rounder and smoother, and so are easier to polish. When wet, as they often are, their colours and patterns are clearly to be seen. On beaches with stones, there is usually a great diversity of types of stones within a relatively small area, minimising the time and effort when collecting them.
In February of 2016, my wife Petra and I were on holiday in the South Island of New Zealand. We had driven our own car down, crossing Cook Strait on a ferry, making our way to Golden Bay then south to Westport, down the West Coast then over Haast Pass to Te Anau and Riverton, right at the bottom of the South Island. Then we headed back north, driving up the eastern coast of the South Island, through Christchurch and Kaikoura then to Picton where we caught the ferry back to the North Island and a six hour car-ride home.
Somewhere between the West Coast and Riverton, we decided we would find out more about polishing stones. We have both always been the type who have walked beaches with our heads down, looking for interesting shells, driftwood and stones. The shells and driftwood usually found a place in the house or in the garden, but the stones that we collected have always been a problem. They just don’t look the same when they’re not wet. They tend soon to be overlooked or lost.
I have an aunt who many years ago used to polish stones from Riverton – my grandparents had a holiday home (“crib”, in local terms) there, at Hendersons Bay, and my family usually spent a couple of weeks there every summer.
I remember the polished stones of my aunt, collected from Riverton – I never knew how she polished them but I was impressed with the results. Petra and I decided to collect some stones on our holiday and try to polish them when we got back home. We ended up collecting more and more stones as we went along, weighing the car down significantly.
Upon arriving home, Petra and I did some internet searching and found out about rock tumblers. We bought three and started out on a journey of learning, of experimentation and of rearranging aspects of our domestic space to make room for it all.
This Blog is a way for me to share our discoveries, to share information, and to help others who start on the same journey. I can be contacted at john.tumblestone@gmail.com – all comments and questions welcomed.
