Used in Australia, described as an essential part of a mix: 4pts. bark to lpt. blue metal (not otherwise identified, presumably an aggregate); to each four gallons of mix add three gallons of water into which has been dissolved 1 teaspoon Sulphate of potash, same of Sulphate of Iron, 1/4 teasp. of Che late of iron, 1.5 teasp. of garden lime and 1/4 teasp. of Copper sulphate (bluestone); good for hardcane dendrobiums and oncidiums. AU85(l)-24