Ever heard about meta stability?
Okay, keep it aside, let me come back to it. But the title is absolutely right. Diamond which is mostly used as jewellery and in past advertised as it is the permanent ornament. But no, diamond isn't permanent.
|Diamond is metastable|
Coming back to metastability, it is a particular excited state of an atom that has longer lifespan than regular excited states of atoms.
Metastability denotes an intermediate energetic state, which is stable at almost every condition and has infinitesimally slow rate of decomposition.
Diamond is a metastable allotrope of carbon, which means it is not stable but appears to be stable at ordinary conditions. We all know, diamonds are formed under very, very high pressure and temperature. And hence it's highest stability is at high pressures and temperatures and not at ordinary room conditions.
The truth is, graphite is the most stable form of carbon allotrope thermodynamically. So diamond and other forms just turn into graphite, just after lakhs of years.
It's pretty long, too long accurately, but the conclusion is diamond isn't permanent as advertised by jewellery companies. Instead, the transformation is infinitesimally slow process and one generation can't observe the change.
What else is permanent? Let me know down in the comments :)