Sand, heat, glass: the whole poem grows out of that small piece of chemistry. In the first stanza the speaker's bones crumble "to sand" and fall "swiftly to the ground." In the second they are "heated / in the immense warmth of my love" until they become glass. It is a clever, slightly eerie way to describe what love costs. The hardest, most supportive part of the body is dismantled, melted down and remade as something you can see through, and something that breaks. Everything after that is a consequence of the first transformation.
The central idea is that openness and vulnerability are the same thing. Glass lets light in, and the heart "shone throughout my chest", so the beloved can see it. That visibility is the gift. But glass is also what shatters. The speaker turns the body into a house, with bones as walls and "glass doors" to open, and invites someone inside: "i held my hand out slowly / for you to safely walk inside." The word "safely" carries the poem's pain, because the rest of the poem shows it was not safe.
The fifth stanza holds the most interesting contradiction. The heart was "always covered with stone / so it shall never fall apart." The speaker has two layers, stone as armour and glass as the truth underneath. Opening the doors "to show you my glass heart" seems to mean lifting the stone aside, yet the poem never describes that moment, or what the other person did. We jump from the open doors to "now." The betrayal or break-up, whatever it was, happens off stage, and the silence between stanzas five and six is where the damage is done. Judging by the text, the poem is less interested in blaming anyone than in measuring the aftermath.
The form is plain and unguarded. There are six quatrains in lowercase, with sparse and inconsistent punctuation, which makes the voice feel like a diary entry or a confession. The rhyme is loose at first, with "sand" and "ground" barely touching, then it tightens: "yes" and "chest" in stanza four, "heart" and "apart" in stanza five, "mess" and "chest" in the last. The chiming becomes firmer as the poem closes, so the ending lands with a click of finality. The syntax is often tangled. "Had lay my glass heart" and "so because a wall of fragile glass, was a heart beneath my fragile chest" make a reader stumble. They also sound like thoughts tumbling out before they have been tidied, which suits a poem about being exposed. The repeated "fragile" is telling too. Even the chest is fragile, so nothing in this speaker is solid enough to hold the heart.
"Glass" is the key word, hammered through the poem again and again: glass bones, glass heart, glass doors, glass walls. The repetition makes the metaphor total, so the speaker's whole body belongs to it. The tense shifts as well. Most of the poem looks back in the past tense, and the last stanza arrives in a bare present: "now i stay silent." After so much shining, transparent imagery, the final picture is small and domestic, a person "crying into my pillow." Glass breaking is usually loud, but here the shattering is described rather than heard, and the quiet makes the loss feel lonelier. The odd spelling of "hallow chest" is presumably meant as "hollow", which completes the picture of an emptied body. The stray echo of "hallowed" might even suggest a sacred space left bare, though that is a possible reading, not a certainty.
The poem is significant for how much it does with one idea. It has no complicated vocabulary, but it carries a single metaphor from the first line to the last without dropping it, and that is harder than it looks. It also gets at something many people feel after trusting someone. The fear isn't only that the heart will be hurt, but that being seen clearly is exactly what made it breakable. Its roughness, from the uneven grammar to the bare lowercase, helps the poem sound sincere.