Mineral sulfur has several different allotropes. For cyclooctasulfur, the most common polymorph is ⍺-sulfur. Other forms are ꞵ-sulfur, which is only thermodynamically stable between 95-120 °C (typically found in volcanic or fumarolic environments), and the exceedingly rare 𝛾-sulfur (or rosickyite). Both of these forms are semistable and revert back to ⍺-sulfur at room temperature. However, there are some cases in which these forms appear anomalously that could indicate the presence and/or activity of microbial life. Some suggest that rosickyite and/or ꞵ-sulfur in these environments are the direct product of microbial activity. Others argue that they are instead due to the presence of organic carbon compounds (some of which can be produced abiotically), which stabilize these minerals. Differences in the occurrence and structure of sulfur minerals may be an indicator of biotic vs. abiotic production.
Rosickyite and ꞵ-sulfur found in non-volcanic/fumarolic locations are typically either direct products of microbial sulfur oxidation, or are due to the presence of biotically-produced organic carbon. [Congruence]
EnvironmentsMagnetotactic bacteria produce greigite more quickly at ambient temperatures than in abiogenic analogue experiments. [Congruence]
EnvironmentsMicrobial influence on geochemical conditions allows rosickyite to form and remain stable in non-volcanic/fumarolic conditions. [Survivability]
Environmentsꞵ- and 𝜸-sulfur (rosickyite) allotropes are stable at low temperatures in the presence of complex organic carbon compounds. [Survivability]
EnvironmentsRosickyite and ꞵ-sulfur found in non-volcanic/fumarolic conditions can be due to the presence of simple, abiotically-produced organic carbon compounds. [Congruence]
EnvironmentsAbiotic organomineralization of S(0) may be a widespread process in many sulfidic environments. [Congruence]
EnvironmentsAbiotic organomineralization of S(0) competes with microbial sulfide oxidation, therefore it may only be prevalent in settings where it exceeds or equals the rate of microbial S(0) biomineralization. [Congruence]
EnvironmentsAbiotic greigite formation in aqueous systems is enhanced by the presence of aldehydes, and is similar in size to biogenically produced greigite in magnetosomes. [General]
Environmentsꞵ- and 𝜸-sulfur allotropes are stable at low temperatures in the presence of simple, abiotically-produced organic compounds. [Survivability]
Environments