Your mom probably likes rings. But she does not want anything as a ring. She wants gold or diamond rings. Gold is yellow metal. The diamond is a transparent stone, a crystal in fact. At first these two elements were rare.
Now we can produce diamonds compressing stones. Also those who own gold have a lot of money. Now, it is the gold rings that are more valuable than the rings with a diamond without gold. Traffickers use this desire to own to raise prices. Thus gold is worth more and more expensive. Diamonds have fallen significantly in price when they could be produced a lot.
My Notes
What would you like to own? Is it easy for you to own it?