separate a population into groups using 3 sets of data at once

Hi there,
I'm working on a population for which I have done 3 chemical analyses that give the concentration of different products in their tissues. The results seem to show that there's a segregation of my samples into 3 or maybe 4 groups.

an example of the 3 main categories simplified (the 4th potential would be in between #2 and #3:
Indiv #1____2_________15__________2
Indiv #2____5_________6___________5
Indiv #3___10_________2__________11
(sorry for this horrible table)

I would like to find a statistical test that would separate my samples into groups using the 3 concentration at once but I'm not sure on how to do so. I usually compare groups.. here, I would like to build groups..
Any help here to find a statistical test/method would be greatly appreciated!
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