The mineral had a cubic crystal structure; chemical analysis revealed that it is mainly composed of SiO2, but also contains up to 12% of carbon and sulfur.

[6] Since many molecules form unstable guests, the symmetry of melanophlogite can change between cubic and tetragonal upon mild heating (<100 °C).

Otherwise, melanophlogite is thermally stable and its physical properties do not change upon 20-day annealing at 800 °C, but it converts to cristobalite after heating at temperatures above 900 °C.

[2] Melanophlogite is a rare mineral which usually forms round drops (see infobox) or complex intertwinned overgrowth structures over sulfur or calcite crystals.

[2] It is found in Parma, Torino, Caltanissetta and Livorno provinces of Italy; also in several mines of California in the US, in Crimea (Ukraine) and Pardubice Region (Czech Republic).