Tracking the Elusive Wild Felspar

Porcelain stone occurs in many of the hills around here in Arita, where the local white granite has weathered down into a softer white to off-white, mixture of kaolin, silica, felspar and specifically sericite. Sericite is a white, plastic mica. This means that it is throwable on the potters wheel as well as vitrifying to a translucent glassy matrix when fired. A very rare and specific combination of qualities.

Today I ventured up into the hills to look for some felspar/porcelain stone deposits that I’m told are all around here. Most were closed because they were worked out of the most precious ultra white material. The deposits around here were very small and used by the potters in the immediate locality. Each little district had its own small mine. This used to give the different villages a slightly different quality to their work. However, ultimately, none of them could compete with the large-scale and very high quality sericite that is being mined at Amukusa, just a couple of hours from here. Economies of scale and the quality of the product, along with increased specialisation of the work force made every one concentrate on producing saleable product and abandon self-reliance.

We can drive up the mountain to the scenic lookout and then park the car and go on foot. This is the ‘Black Hair Mountain’ and I’m told that it is a very spooky place. It’s a dark, wet and cloudy day and the Mountain is shrouded in mist. I’m not spooked, because I don’t believe in ROUS ‘Rodents of Unusual Size’ ‘Fire Swamps’ and ‘ Lightning Quicksand’. The Princess and I press on, the track is very wet and slippery after last weeks constant rain. In dry weather we could have gone a bit farther by car, but not today. So we walk. The little track wanders around the contour of the hill and would have been quite manageable at the time when it was in use and repaired to handle constant traffic of the ore down hill. We head off up the hill on a stone staircase to get to the top. It takes some time before we realise that we are on the wrong track. We go back and try again.


This time with more luck. We find a diagrammatic map along the way that shows us the location of the old mine, but not in much detail. Up the hill, over the bridge across the river. Through the ‘Fire Swamp’ and the valley of ‘Lightning  Quicksand’. We keep going until we reach the water fall and then it shouldn’t be too far, according to the map, and then there ought to be another bridge to cross back to the other side of the river. Through Dead Mans Gulch. Then up along The Valley of No Return,  up the sacred mountain to the water falls and then a righthand fork should lead you straight to it. We do and it does – more or less.

Except that I lost my nerve when we didn’t find any sign of a mine after such a long trek. The road became very narrow and washed out after some very heavy rain. There were trees across the track. The sound of crunching twigs under foot coming from the forest around us and an owl hooted, while a black raven swooped overhead. It was quite obvious that nobody had come this way for a long time. This was indeed the path less trodden!

We retraced our steps and consulted the map. This time I photographed it. It seemed that we were almost there when we turned back. We tried again and this time found that the turn off to the old mine was just another 100 metres up and around the side of the mountain. What we found was a rusty steel mesh gate with large red warning signs all over it. I can’t read Japanese, so what I read into it, was that this is the place that you are looking for. ‘Keep going, it’s just a little way on from here”. Almost there!

Of course it could also have said. “This is the old dangerous mine site. No Entry! or  “proceed with caution!” Or maybe it said that the bridge is closed because if you tread on it, it will collapse!

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So we did. It meant swinging out over the stream to get around the gate. Then onward and upward. We knew that we had reached the correct place when we found the boarded up mine shaft entrance.

There was plenty of spalls all around on the ground outside. So no need to go in. The material looks just the same all over the world. Similar colour and texture, similar fracture angles, but the hardness varies due to the amount of weathering and decomposition of the felspars down into kaolin.

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The softer the stone, the greater the degree of weathering and the more refractory it will be with an increased kaolin content. so it will be more plastic, but less fusible at high temperature. The harder it is, the more fusible it will be and the more vitreous at high temps, but the less plastic to work with. Somewhere half way between is a good compromise, or a blend of two different stones will achieve the same result.

This stone is quite hard to break and is probably quite high in felspar, sericite and quartz. It feels to me to be a useful glaze stone. We walk back down the mountain, happy trekkers with a pocketful of samples. I learn the next day that the reason that this site was closed, was because there was a mine collapse 30 years ago and a number of miners were killed there. Very sad, but not spooky.

News travels fast. The next day, Mr. Akio Kanaiwa san. A retired geologist and lecturer in ceramic chemistry from the Ceramic University here, specialising in porcelain stone, calls in to see me. Miyuri san, the local cultural guide here in Arita has met him and mentioned me and my special interests to him. We get along very well and in just a few minutes we manage, even with so little language, to exchange our views and knowledge about porcelain stones. We both can read chemical analysis, X-ray micrographs, SEM data files and ceramic Seger formulas. He shows me some of his research that he has brought along. As he flips through his files. All in Japanese. I can read them out to him. He realises that I know exactly what he is trying to tell me in chemical terms. The only  thing that I can’t do is understand his excited Japanese Arita dialect. It turns out that I am the only person that he has met that has his own Denver cell for froth floatation separation and purification of ceramic minerals. The only difference in our techniques is that he uses pine oil and I use kerosene. Amazing!

We arrange to go on a geology excursion the very next day with Tsuru Miyuri san as our translator. It turns out to be a very full day, as Akio Kanaiwa san has a quite a few sites that he plans to take me to. I am thrilled. We both really enjoy our time together with Miyuri san. She is amazing, such good value. She is so knowledgeable about ceramics in Arita and her English is excellent, so she is so good to have along on a trip like this. We go to site after site. He really knows his stuff. Through Miyuri, we exchange ideas and analysis data.

At one point we all have to stop and laugh, as Kanaiwa san and I find ourselves agreeing on the importance of secondary mullet crystals in the development of strength, translucency and slump resistance in porcelain bodies. Miyuri san, who is quite faithfully translating our conversation, back and forth, is stunned and mystified by what she is having to say, as she doesn’t understand a word of the technology involved. When Miyuri doesn’t know the word or a suitable work-around sentence to convey the meaning, Kanaiwa san and I revert to writing the chemical symbol or formula. It’s a wonderful, positive, cultural exchange.

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Miyuri san explains to Kanaiwa san how I collect most of my materials where I live in Australia and my amazement at how similar they all are to these minerals that we are looking at there. The only difference is that these minerals are mostly much cleaner and lower in iron. Only one of the sites is still being used, an open-cut quarry where an interesting felspar/quartz stone is being mined for use in electrical insulators and industrial tiles. It is called ‘The Dragon Gate’ mine. There is a lot of iron present here, but it is in bands and veins, so could be sorted out or extracted.

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Our last visit in the afternoon was to a glaze stone mine in Takeo. The ‘3 splits’ mine. This name causes a lot of muffed laughter. Apparently it is not really the true name of the mine. It is named after the combination of hills and valleys that look like the gap between someone legs. This is a name that can’t be said by a lady. A more literal translation might be ‘fork’, as in ‘a fork in the road’, but more likely ‘crutch’, as in the gap between a persons legs? I don’t end up knowing what it is called. Perhaps it’s 3 cracks? Because if you go up the crack it ends in a tunnel?

No one will say it in English. So I’m calling it the 3 splits mine.

Kanaiwa san says that I look like Indiana Jones or Harrison Ford in my hat. I reply that I can’t afford a whip, but my name is Harrison.

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There had been several attempts at mining here over the last few hundred years. Some open-cut and others in deep shafts and drives. All closed now. Again, the shaft is barred by a wire fence that declares that this is the correct place alright. The fence seems to have fallen over at one of the mine shafts, so I can’t read the sign that might say ‘don’t enter’. So there is nothing to stop me. – Except the fact that it is all flooded inside.

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The water is a pretty translucent  pale blue. Just like blue celadon over porcelain!

I explain that this is the most dangerous site that we have visited yet. Not because of the risk of mine collapse, scrambling through flooded water or drowning, but because of the crumbly asbestos fence!