It should have been:
>Gold, Silver, Platinum
>Diamond, Pearl, Crystal

And yet it was reversed? Why? Platinum is a precious metal like Gold and Silver. Crystal (leaded glass) is a miscellaneous material used in jewelry like pearl (substance from animal source) and diamond (a rock).

There is no reason or rationale for fucking up the naming this badly. It is an embarrassment and a permanent stain on the series.