1. Violent attack is of clear concern to black politicians.For the above cases, I couldn't find a meaning of "of" in Dictionary.com that make sense to me.
2. The gas and oil pipelines that run through Georgia are of strategic importance to Western Europe
3. This by itself is of no help here.
Is this clearer: " stone of the size of a pea"? "His eyes seemed of a strange color" With an "of" we separate an object and the properties thereof. Let's take your version of the second sentence, which says: "T hey [gas and oil pipelines] are strategic importance to Western Europe.
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