The Gabbro Calcite is a ribald poetic form intended to express pleasure with Faret Alexandritepicture-jaspers, originating in The Doorstop of Spiny-Dogfishes. The rules of the form are applied by poets to produce individual poems which can be recited. The poem is a single tercet. Use of ambiguity is characteristic of the form. A form of parallelism is common throughout the poem, in that certain lines use the same placement of allusions. Each line has five feet with a tone pattern of uneven-even. Every line of the poem has an initial caesura.