Solarian truesteel is an ore native to Solaria, fourth of the Seven Heavens of Mount Celestia. A pure iron, Solarian truesteel needs no alloying for strength, and is as strong as steel when used to create objects.
When used in a weapon, Solarian truesteel provides a +4 enhancement bonus to confirmation rolls for critical hits, and counts as cold iron with regard to DR. It has hardness 11 and 25 hp per inch of thickness, and weapons made of Solarion truesteel are 3x normal price and must be masterwork.
- Book of Exalted Deeds, pg.38