The pearl in this poem is a piece of jewelry, but also a question about who gets to profit from pain. The speaker begins by calling it a "god-shaped hole / filled with suffering," and then turns on the wearer, someone who hangs it around her neck as if she has a right to "the gleam of others' tears." The tone is sarcastic and accusing. The speaker seems to be addressing a person who tells herself comforting stories: that the oysters sleep well, that a grain of sand is too small to matter, that it is silly to see "a world of pain" in something so tiny.
That last image carries the poem's sting. A pearl begins as an irritant, and the speaker flips this around, suggesting that the real irritation is the wearer's own "microscopic" complaints, which can't possibly block out the light. The mood is bitter and confrontational, with a dry, mocking edge. The speaker refuses to let beauty float free of the suffering behind it.