ACROSS
1.  Dig around a naval compound yields mineralogical treasure (10)        
6.  In short, your typical average marine content  (4)                
9.  Flooding by rustic lane (10)                
10.  Asbestos source has an inside admirer (4)
12.  Process steely resolve from a loud heater (5,7)
15.  Dark flower bursting out down hillside  (4,5)         
17.  French cloth production has come a long way! (5)
18.  Initially, capital left penniless from foreign growth (5)        
19.  Rip the corners!  Such blue composition! (9)
20.  Allocation for women only class by Yorkshire river (12)    
24.  See 25 across.
25.  In a solution, heat-related charges may come with no hydro bills (10,4)
26.  Better assume they’re hidden in a timely fashion (4)
27.  Heard 17 ac. worked in or on a Celtic home (5,5)

 

DOWN
1.  No need to go down this shaft (4)
2.  Load and fold (4)
3.  Low and cold, pressing into action (5,7)
4.  Out of the blocks, Great Britain profits (5)
5.  They’re dry but mobile and capable of shape shifting (4,5)
7.  Donning messy head gear underground might blow you away! (3,7)
8.  Often seen doing trav’s across a rift (10)
11.  Dangerous perch, alternatively high and dry (2,2,3,5)
13.  Obstinate, yet having a sparkling attraction (10)
14.  Loaves and fishes by a heavenly, tranquil setting (5,5)
16.  Where Noah lazed around looking for bottom feeders (5,4)
21.  No charge in sedition so you can come and go (5)
22.  Brilliance shown by it in passage was hilarious (4)
23.  Simply used for hunting in southern greenstone (4)