Micro-scratch　tests　have　been　carried　out　on　borosilicate　K9　glass　using　a　Rockwell　C　diamond　indenter　with　a　spherical　tip　radius　105　μm　in　order　to　study　deformation/damage　regimes　and　microcracking　patterns　of　K9　glass　with　increasing　normal　load.　The　abrupt　changes　of　test　data　together　with　optical　microscopy　observation　can　be　used　to　determine　three　transition　loads　corresponding　to　initiation　of　sub-surface　median　crack,　onset　of　surface　ring　crack,　and　lateral　cracks　reaching　the　surface,　respectively.　Based　on　linear　elastic　fracture　mechanics,　fracture　toughness　obtained　from　scratch　test　under　a　low　driving　speed　and　a　suitable　fitting　range　of　nominal　size　is　found　to　be　0.85　MPa•m1/2　for　K9　glass,　which　is　close　to　0.82　MPa•m1/2　obtained　from　Vickers　hardness　technique,　making　micro-scratch　a　powerful　means　to　assess　fracture　toughness　of　material,　and　opening　new　application　of　scratch　test　as　a　quantitative　method.　©　2019　Elsevier　B.V.