... :silver gold expanded Size:1-3mm 4-7mm Hardness:1.5-2.8 proportion:2.4-2.7 Usage:heat resistant and ... two types: one is Silver-grey type ( Fe2O3 content around 5-8%, similar with South Africa vermiculite); the other type is Golden ... .2, for silver gray vermiculite,its PH is 8.5-9.5, that's to say, golden vermiculite is more neutral. In ...