Carbon calabashes in a shock-produced carbon melt

Carbon calabashes similar to those reported during decomposition of CH4 between 900 and 1050 °C also formed after thermal decomposition of dolomite, CaMg(CO3)2 in a low-angle impact experiment that produced a carbon melt and complex gas phase between 2700 and 3700 °C. The interrelationships among various carbon forms in this experiment support that the calabashes are quenched carbon-melt bubbles at high gas to liquid ratios. Carbyne forms of carbon that crystallized within the quenched-liquid shell of the bubbles did not require a spiral growth mechanism. Carbon calabashes are an oddity but not a new form of elemental carbon.