We know that diamond is the hardest naturally occurring substance and so it is much much stable as compared to the other allotrope of carbon i.e graphite as per their structure apparently .But,why then then the bond order of graphite(1.5) is greater than diamond(1).As we know Bond Order is directly proportional to stability.Please give appropriate explanation.

diamond is a "COVALENT NETWORK SOLID" but graphite consists of perfectly plane sheets of GRAPHENE 

The reason is not so simple.At first we shall look into the structure of diamond and graphite. Diamond is a covalently bonded arrangement of carbon atoms with a three dimensional structure,whereas graphite has an hexagonal array with double bonds in it.but the compactness or the packing arrangement of diamond is such that the distance between two adjacent atoms is very very less,hence more energy is required to break carbon carbon bond in diamond.... also that stability is a complex phenomena which you may understand in class 12 thermodynamics and higher studies... also over here stability is inappropriate word and hence it should be more inert or less inert

But,your answer is very confusing.Please elucidate your explanation.