Glassy igneous rocks (i.e. obsidian) are cooled very rapidly.
        
             
        
        
        
Answer:
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They have a coarse-grained texture.
        
                    
             
        
        
        
A. Neutral water 
Less than 7 is acidic (which has 6 letters, 6< 7)
More than 7 is alkaline (which has more than 7 letters). Alkaline = basic 
7 is neutral