Historic or historical

 This is a historical event.  
(one that happened in the past)

 This is a historic event.  
(one that is important in history, e.g., the Moon landing)

 He was a historical scholar.  
(A scholar who studied history) 

 He was a historic scholar.  
(A scholar who was important in history, e.g., Homer) 

 The bones were of historical significance.  
(significant from a perspective of history, i.e., possibly worthless but important to study history) 

 The bones were of historic significance.  
(very significant, i.e., important in history)