This is a tiny poem about a trick of seeing. The speaker looks at a quarry, a place where rock has been cut open and left bare, and notices that even though it is only half a mile away, it already looks blue. We usually expect that kind of blue haze from faraway mountains or horizons, so there's a small surprise in seeing it so close.
The speaker doesn't tell us how they feel, but the tone seems quietly pleased and curious. The word "already" matters most. It suggests the speaker is a little amazed at how quickly distance changes things, how soon a hard, gray, scarred place softens into something almost beautiful. The mood is calm and observant, with a hint of wistfulness, since the quarry feels both near and out of reach. In just three short lines, the poem asks us to slow down and notice what our eyes do with the world around us.