The most common and most likely answer to this crossword clue is the 10 letter word GADOLINITE
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The straight part
We know that "Silicate" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case silicate = gadolinite.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does GADOLINITE mean?
GADOLINITE noun- A dark, vitreous mineral that is a complex mixture of silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron, with the chemical formula (Ce,La,Nd,Y)2FeBe2Si2O10.