I found both forms (with and without "a") on the Internet. I don't know which one is more acceptable.

Is it an idiom?


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2 Answers 2


As this Ngram graph shows, neither expression is particularly common: in my opinion, neither is idiomatic either.

Reading the full text of the two articles, there are sufficient grammatical errors to make me doubt that the author or either article is a native English speaker.

There are two similar idiomatic expressions: "as solid as a rock" occurs more frequently, and "rock solid" is very common.

Note that there are differences between British and American English in the use of the words rock and stone.


Both are correct.

solid like stone (stone - mass noun)

solid like a stone (stone - countable noun)

[ (as) solid as a rock= having a very strong basis, strongly built (not likely to break/fall) ]

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