I think it is
Platinum
Explanation
One thing to keep in mind is that Atomic number of platinum is 78
Split me into 3, and you will feel like iron,
78/3 = 26. And 26 is the atomic number of Iron.
But you see I am much more stronger than it.
Yes. Bulk Modulus of platinum is 230 GPa while of the iron is 170 GPa
Split me into 6, and you will feel like alluminium,
78/6 = 13. And atomic number of aluminium is 13
But you see I can't be softened as easy as it.
Aluminium is more malleable than platinum
I stand next to a precious golden treasure,
In periodic table, Platinum is right next to Gold which have atomic number 79
But I am still much more valuable than it.
Yes, I think we all know that.