White crystals of the rare silica-hydrocarbon minerals chibaite (IMA 2008-067) and bosoite (IMA 2014-023) from the type and only known locality worldwide for both species: Arakawa, Minamiboso City, Chiba Prefecture, Honshu Island, Japan. Chibaite and bosoite can't be visually differentiated. Natural analogues of synthetic clathrate MTN with hydrocarbon molecules such as methane, ethane, propane, and 2-methyl-propane contained in its cage-like voids. Chibaite and bosoite are also described as a clathrasils. Ex Alfredo Petrov specimen. — Photo: David Hospital · CC BY-SA 4.0
Chibaite
A rare silica clathrate — a cubic SiO₂ framework that cages small hydrocarbon molecules like methane and propane inside.
Intro adapted from Wikipedia (CC BY-SA).
Chibaite is an IMA-recognized mineral species in the organic mineral class, with the chemical formula SiO₂·n(CH₄,C₂H₆,C₃H₈,C₄H₁₀) (nmaₓ = 3/17).
It crystallizes in the cubic crystal system (space group Fd3).
Key properties: Mohs hardness 5.5–7; specific gravity 2.03.
IMA symbol Cib, IMA status: approved, named in 2008.
Occurs as veins cutting tuffaceous sandstone and mudstone in forearc marine sediments deposited near the plate margin of the Paleo-Izu arc and the triple junction of the Pacific, Philippine Sea, and North America plates.
It is found associated with DOH-type silicate clathrate, calcite, quartz, opal-A, pyrite, epistilbite, clinoptilolite.
The name refers to the Chiba Prefecture in Japan where the first samples were collected.