ScAlMgO4　(SCAM),　which　can　be　used　as　an　epitaxial　substrate　material　of　GaN　in　power　devices,　faces　the　challenge　of　achieving　a　high-quality　surface　by　ultra-precision　polishing　due　to　its　brittle　and　easily　cleaved　characteristics,　which　are　closely　associated　with　its　mechanical　properties.　The　micromechanical　properties　of　SCAM　single　crystals　were　evaluated　by　nanoindentation　and　microscratch　tests　using　different　indenters.　The　elastic　modulus　EIT　and　the　indentation　hardness　HIT　of　SCAM　obtained　by　nanoindentation　were　226　GPa　and　12.1　GPa,　respectively.　Leaf-shaped　chips　and　the　associated　step-like　planes　of　SCAM　can　be　found　in　the　severely　damaged　regime　during　scratching　by　Berkovich　and　Vickers　indenters　with　sharp　edges　due　to　the　intersection　of　intense　radial　and　lateral　cracks.　The　fracture　toughness　(Kc　=　1.12　MPa·m1/2)　of　SCAM　can　be　obtained　by　using　a　scratch-based　methodology　for　a　spherical　indenter　based　on　linear　elastic　fracture　mechanics　(LEFM)　under　an　appropriate　range　of　applied　loads.　An　optimal　expression　for　calculating　the　fracture　toughness　of　easily　cleaved　materials,　including　SCAM,　via　the　Vickers　indenter-induced　cracking　method　using　a　Berkovich　indenter　was　recommended.　©　2024　by　the　authors.