The cosmochemical classification of the elements

The present cosmochemical study divides the elements into four groups: refractory, moderately volatile, highly volatile, and siderophile, with the former three respectively condensing at temperatures higher than 1300-1400 K, between 670 and 1300 K, below 670 K. In the case of siderophiles, the essential condition is their being more easily reduced to metal than Fe. The siderophiles tend to behave as a cohesive group, occurring primarily as alloys in the FeNi-metal phase; their abundance and distribution, however, also appear to depend, in part, on their volatility.