"A geologist's song 06" joke

The geology poem
Ode to Olivine in Thin Section, a poem by Brenna Lorenz
In basalt a lurid green
Bespeaks the savage olivine;
Mantle's child, born of fire,
Restless in the open air,
Little beads of anger bear
The torture of desire.
Silica upon its face
It suffers, helpless, in disgrace,
Its powers of reaction bound
By solid's bond and cage,
In agony confined to rage
Unstable and unsound.
Its birefringent power plays
The sifted light to rare displays;
The haunting, primal colors tell
Of fire and fury's flag unfurled,
Flag of fluid, nether world,
Beneath the fragile shell.