Yesterday a 3lb barrel of stones from Kakanui’s Seadown Beach finished the tumbling process. This beach lies just two kilometres north of the town of Kakanui in North Otago. An introduction to the beach is provided in TumbleStone2. These 61 stones were previously tumbled in 400 silicon carbide grit, then some spent time tumbling in the finer 600 grit. I have found that jaspers and stones that consist of bands and patches will take a polish better if they have the extra tumble in the finer grit. The polish tumble lasted for just under 12 days, followed by a two day burnishing tumble in borax.
In general, close-up photos of polished stones can often reveal wondrous shapes and patterns and structures, turning a sometimes ordinary stone into an aesthetic treasure. But sometimes the close-ups can also reveal flaws that are not detected by the naked eye. I picked out six of the polished Kakanui stones to look at more closely in this Post. The ones chosen had caught my eye, and seemed to have polished well. However, it turns out to be a challenge to achieve a completely smooth polished stone. Closer examination reveals tiny rough patches or holes in all of them. Sometimes this is because of the fractured nature of the stone and my reluctance to reduce its size too much. Sometimes it is because I have not picked up the rough patches and holes when deciding to move the stone to the final polishing stage.
The first stone (photos below) caught my eye because of the white quartz segment within it which shows on both sides. It is the second largest of the six stones, four centimetres high and two-and-a-half centimetres at its widest. It is probably a quartzite. I have been following it eagerly through the various stages of tumble-polishing. It is perhaps the most smooth of the six featured in this Post, but the close-ups still reveal an occasional tiny scratch (see the first of the close-ups of the B Side).
The next stone is very dark in colour though it comes alive in bright sunlight – then it is apparent that there is silvery-grey hematite in it. The photos below make it appear less dark than it is in person. Maybe this is a jasper stone, perhaps related to the limonite prase that can be found along this part of the North Otago coast. I thought this stone was very smooth but it turns out to have a shallow hole in the middle of the B Side. It’s tempting to return the stone to a grit tumble and remove it, but that then reduces the stone’s size. It is currently three centimetres long and two centimetres wide.
The third stone is a similar size to the previous one, and is probably a jasper. I find this light-coloured form of jasper to be very appealing (see here for a Post with other examples of light-coloured jaspers from Kakanui). But, like many jaspers, it is difficult to obtain a smooth and shiny outcome. This stone came out of the tumbler looking and feeling very good, with just a little roughness associated with the dark vein on the A Side. However, the photos below show a number of tiny rough areas in different parts of the stone.
Some stones hide their tiny rough areas along their edges. “imperfections” The fourth stone is a bright and interesting one that has generally polished well. However, at the bottom of the close-up of Side B, a line of roughness is apparent. It is difficult to eliminate such roughness as further tumbling in grit tends to move such an edge back rather than cause it to disappear. In many ways it does not detract from the two main faces of the stone, but it is annoying when felt as a finger moves over the stone. This stone is approximately the same size as the second, third and fifth stones.
The fifth stone is of a slightly different shape, more elongated, and is likely to be a quartzite. It has patches and veins of a light brown, and a tiny green vein on Side B, providing visual interest. Once again, the stone appears smooth and polished but the close-ups reveal tiny “imperfections” not apparent to the naked eye.
The sixth and final stone is the largest, five centimetres high and four centimetres at its widest. It is a yellow quartzite, a fairly common stone on Kakanui’s Seadown Beach (see this Post for other examples). These quartzites are often fairly smooth already when found on the beach, but sometimes, after some tumbling, they can be found on close inspection to have tiny holes in them. Further tumbling will make the holes disappear but only at the cost of reducing the size of the stone. The close-up photos of the sixth stone reveal not only the tiny crystals in it but also a small number of tiny holes which are actually very difficult to discern with the naked eye.
In general, the flaws detected in the close-ups of these stones do not detract from an experience of them as interesting and smooth stones. But I feel the need to conduct my inspections between tumbling stages more carefully to try to improve the finished result. There are always exceptions of course, where a really interesting stone has a hole or crack too large to eliminate, and when I need to decide to live with less than a smooth polish in order to enjoy the stone.
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