Rock and rubble finally dumped on specified place (8)

I believe the answer is:

andesite

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'rock' is the definition.
(I've seen this before)

'and rubble finally dumped on specified place' is the wordplay.
'finally' suggests the final letters.
'dumped on' means one lot of letters go next to another.
'specified place' becomes 'site' (site is a kind of place. I am not sure about the 'specified' bit.).
The final letter of 'rubble' is 'e'.
'and'+'e'+'site'='ANDESITE'

Can you help me to learn more?

(Other definitions for andesite that I've seen before include "Volcanic rock from South America" , "Rock from Argentine" .)

I've seen this clue in The Guardian.

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