Abstract: A novel lubricant composition is disclosed, which contains not less than 0.1% by weight of at least one calcium ferrite having the following general formula:Ca.sub.x Fe.sub.y O.sub.x+(3/2)ywherein x is 1 or 2 and y is 2 or 4, provided that y is 2 or 4 when x is 1, and y is 2 when x is 2. The calcium ferrites may be monocalcium ferrite, dicalcium ferrite or hemicalcium ferrite, produced by mixing iron oxide and a calcium compound in a molar ratio of 1:0.5 to 1:2 and fusing them by heating at a temperature of 1200.degree.-1400.degree. C. The resultant material contains not more than 5% by weight of the whole, of ferric oxide, silica and alumina as impurities. The calcium ferrites have a maximum particle size of 100.mu., preferably 0.15.mu.. They can be used as such for lubricant purposes, or can be incorporated in a lubricating oil or grease, such as a mineral oil, in an amount more than 0.1% by weight and preferably more than 1% by weight.