Patur -welcome back
Chemically Identical in what color it is. It is the exact color of the indigo. I do not know chemistry but the way someone explained it to me is that there is something in the chilazon that when mixed with purpurase which has some sort of reaction with the air that causes the dye to stick. Now Kla Ilan has the same purpurase stuff just the other chemicals are slightly different. To proove that they are different i can tell you that they show differences when exposed to bleach. NOw regarfing the gemaras test that does not work means we either are doing the test wrong or maybe nishtanu hateva or maybe they make the kla ilan differently these days. I don’t know. But it does not say anything about the techeles being that even if you think the murux is not the techeles we still know this is the kla ilan.
NOw there is evidence that the murux was used as a dye 2000 years ago from digging things up. So if the gemara goes out of its way to tell us that there is something identical why does it only mention the indigo and omit completely the murux which was used in those days and is the exact same color?