The first Post in this series described Stage One, Stone Collection. To illustrate the next six stages in the tumble polishing of stones, I decided to select 40 of the stones I had collected at Riverton in early November. I chose a range of sizes, colour and quality. The following are photos of all 40 stones, first of all how they appear dry and then how they appear wet. This demonstrates how wetness brings out colours and patterns much better.
Stones 1 to 5:
It will be interesting to see how much of each stone is worn away throughout the tumbling process. Stone 1 (far left) is about 8 cms long and about 5 cms wide at its widest point (using the graph paper it is lying on in the “dry” pic above). Stone 3 is about 6 cms long and 4.5 cms wide, while Stone 5 (far right) is just over 7 cms long and is 3 cms wide. I think that Stone 1 is of volcanic origin, as it has small specks in it that would have originally be gaseous pockets, and will turn out to be similar to another Riverton stone I polished recently (below).
Stone 2 is also probably volcanic in origin, having similar specks. Stone 4 looks like a conglomerate (which simply means it consists of small rounded stones cemented together in a fine-grained matrix). [As its surface became clearer after some tumbling, I decided Stone 4 is in fact a breccia, composed of angular fragments.] Stones 1, 2, 4 and 5 would be too big for a 3lb barrel.
Stones 6 to 10:
These are progressively smaller, with Stone 6 (far left) being about 6 cms long and 4 cms wide. Stone 7 could be argillite (a kind of mudstone subjected to heat and pressure) or epidote (green coloured rock), Stone 9 is a breccia (which simply means it consists of broken fragments of very small stones) and Stone 10 is another conglomerate.
Stones 11 to 15:
The progression to smaller continues. Stone 14 (second from right) is a pink granite that is just over 5 cms long and is just under 4 cms wide at the top. Stone 12, a quartzite, demonstrates how wetness brings out the nature of a stone. Dry, it appears a bland white. Wet, patterns of colour in a strand-like formation become visible with a subtle depth being present. Stone 15, which could be argillite, has an interesting wavy band of white silica.
Stones 16 to 20:
Stones 18 and 19, both about 4 cms long, are potentially quite spectacular. Stone 18 has a number of different coloured bands. Stone 19 contains contrasting black and white sections, and it will be interesting to see if these erode or polish differently.
Stones 21 to 25:
Stone 25 (far right) has some interesting bands that will be brought out by the tumble polishing, but Stone 22 (second from left) may turn out to be even more interesting. The white on the surface of Stone 23 (middle) may be worn away in the process it goes through, but there may be interesting patterns underneath.
Stones 26 to 30:
Stone 26 (far left) is 3.5 cms long and just over 2.5 cms wide. Its two-toned character attracted my eye on the beach. White is a colour that always stands out on the beach too, Stone 27 being a white quartz with a couple of dark intrusions.
Stones 31 to 35:
Stone 31 (left) may be part-jasper, and Stones 32 and 34 are probably varieties of jasper. Stone 33 has interesting reddish protuberance that caught my eye on the beach. Stone 35, white quartz, is 3 cms long and just under 2 cms wide.
Stones 36 to 40:
The smallest stone, Stone 40 (far right), jasper, is 2 cms by 1.5 cms. Up to 20% of a stone may be worn away by the tumbling process so not much may be left of this at the end. However, small stones are good in a tumbling barrel as they “carry” the grit and polish to the larger stones.
I weighed the 40 stones on a set of scales I have in my stone tumbling shed. First placing the empty container on the scales, I moved the setting back to zero so that only the weight of the stones would be indicated = 1605 grams (3.5lbs).
I will weigh the stones after each stage of tumbling to see how much of them is worn away.
The next Post in this series describes Stage Two of tumble polishing, the 100 grit tumble.
