There are 27-steps to process raw clamshells into Go stones.
1.Collect raw clamshells. (Sand pump boat suctions clamshells from the sea bottom. Shells are mined in very deep sedimentation, which is several hundred years old. Today, we no longer collect them because Hyuga clamshells are no more available.)
2.Select and sort raw shells. (Discard bad shells)
3.Measure the thickness of raw shell.
4.Mark the cutting-out position on the shell.
5.Cut out.
6.After cutting out, separate shells based on the color.
7.Measure the thickness. Select and sort cut-out shells.
8.Surface polishing. (First, roughly)
9.Select and sort polished shells.
10.Surface polishing (Secondly)
11.Select and sort polished shells.
12.Finish one side of the shell. (Surface polishing)
13.Selection and resorting.
14.Finish the other side of the shell. (Surface polishing)
15.Selection and resorting.
16.Polish by hand (We spend long hours for this process. We can polish only 20 stones per 1 hour)
17.Smooth the edge of stones.
18.Dry under sunshine.
19.Breaching.
20.Dry under sunshine
21.Polish in barrel-shaped machine (Every stone polishes with each other.)
22.Drying.
23.Sort by thickness.
24.Selecting and resorting to find out damaged, bad-shape, defective stones.
25.Selecting and resorting (Grading) One stone is checked 2 to 3 times in this process.
26.Final selection and resorting. 27.Complete as one product.

*All these process require high level of skill and long experience.