How platinum deposits form - sinker vs floater

https://youtu.be/mEWKXFvczCo?si=0VwKRKv-bxCyq12d

0:15 both Platinum and palladium are common in the earth's crust, but mines for them are rare.

1:27 there are two theories of how deposits are fomred - sinkers and floaters 

2:13 these mines have 15 to 20 g of platinum per ton of ore 

2:36 "cumulate" rocks form by density sorting

2:47 Or, crystals may form at the outer edges of a magma intrusion as the boundary layers cool