Iav yog feem ntau 6.5 ntawm Mohs nplai. MoHS hardness yog ib qho kev ntsuas ntawm lub hardness ntawm cov zaub mov, uas tau muab faib ua 10 qib, ntawm 1 (mos) rau 10 (nyuaj tshaj). Lub hardness ntawm iav yog nyob ib ncig ntawm 6.5, uas txhais tau tias nws tuaj yeem tiv thaiv kev siv tshuab xws li khawb, nias lossis sib tsoo.
Ib qho ntxiv, lub hardness ntawm iav kuj tseem tuaj yeem ntsuas tau los ntawm lwm cov qauv. Piv txwv li, lub saum npoo tawv ntawm tsis kho cov iav yog li ntawm 6H, thaum lub hardness ntawm tempered tuaj yeem ncav cuag 9H. Lub mohs hardness ntawm tsev neeg lub khob yog 5.5, sib raug rau HRC hardness ntawm 61.7.
