A man rubs his belly and gets older. That is the whole of the first stanza, and the way it is cut makes it sharper than it looks. The line break falls after "I grow," so for a moment the word suggests the belly swelling, a comfortable, well-fed kind of growth. Then the next line drops "old and ugly" on top of it. The gesture of contentment turns out to be the gesture of someone idling while time works on him. The speaker doesn't dress this up. "Ugly" is a blunt, almost schoolyard word, and he applies it to himself with a shrug.
The second stanza sets out a yearly rhythm. "All winter I am broke" is flat and factual, and "broke" does double duty, meaning both out of money and, quietly, broken. Summer brings a reversal: "like a child / I dig for gold." This is the poem's only simile, and it matters. The speaker doesn't dig like a professional, grimly and for profit. He digs like a child at a sandpit, with total faith that something shining is just under the surface. The title, "Prospector," lets us read that faith in two ways. It evokes the old figure of the gold-seeker, a gambler and dreamer, but here the dream has shrunk to one aging man with a spade, poor in winter and hopeful again every summer. The present tense helps. Nothing is said to have happened once. It happens every year, and the repetition makes the hope look both touching and a little foolish.
The last stanza delivers the punchline, and it is unsettling: "the earth going to pieces / in my pocket." What the digging yields is not gold but loose earth, crumbling in the speaker's pocket. The phrase "going to pieces" is normally used of people who are losing control, so the poem lends the ground a human breakdown, and the speaker's own decline seems to seep into it. The sound of "broke" in the middle stanza returns as "pieces," as if the poem's two kinds of breakage were being answered by a third. There is also a second possible meaning: the earth itself, the whole world, is falling apart, and he is carrying it around in a small, ordinary place. The poem doesn't choose between these readings, and the ambiguity is what keeps the ending alive after the final word.
The form is as pared down as the speaker's finances. It is free verse with no end rhyme and no regular meter. There are no capital letters and no punctuation, so the sentences run without stopping, like speech that never bothers to finish itself. Line lengths alternate between longer and shorter, and each stanza ends on a short line of about four syllables: "old and ugly," "I dig for gold," "in my pocket." These endings land like small drops, a stepping down at the close of each thought. There is also a buried chime between stanzas, since "old" in the first and "gold" in the second are true rhymes, separated by space. The pairing is a neat piece of irony, because what he finds in himself is age, and age is the only gold he is certain to accumulate. The consonants help too, with the hard g of "grow," "ugly," "gold" and "going," and the clipped p and b of "belly," "broke," "pieces" and "pocket," which give the lines a dry, percussive feel.
The central idea is that hope and decay run side by side and neither cancels the other. The speaker's summer childishness doesn't make him young, and his winter poverty doesn't stop him digging. The seasons suggest renewal, but the poem keeps the body moving in one direction only, toward old and ugly, toward pieces. Even so, the tone is wry rather than despairing. A man who can call himself ugly and then admit he is out digging for treasure has a sense of humor about his own situation.
That balance is what makes the poem worth reading. In under thirty words it holds comedy, poverty, play and the fear of ending, and it never explains any of them. It trusts a belly, a spade and a pocket of crumbling earth to carry the meaning, and they do.