What does coffinite mean?
Coffinite is a rare, black, uranium-bearing mineral with the chemical composition of a hydrous uranium silicate, commonly written U(SiO₄)₁₋ₓ(OH)₄ₓ. It crystallizes in the tetragonal system but almost never forms visible crystals; instead it appears as opaque, sooty or microcrystalline coatings, cement, and replacements within sedimentary rocks. Coffinite is economically significant because it is one of the main ore minerals in sandstone-hosted uranium deposits, particularly in the western United States, where it typically forms under reducing conditions in association with organic matter and pyrite. It often occurs alongside uraninite (pitchblende), another major uranium ore mineral. The mineral was named in honour of the American geologist Reuben Clare Coffin, giving it one of the more memorable names in mineralogy. Strictly a specialist term, coffinite is encountered mainly in mineralogy texts, geological survey reports, and literature on uranium exploration and nuclear-fuel raw materials.
nounA rare black uranium-bearing mineral, a hydrous uranium silicate (U(SiO₄)₁₋ₓ(OH)₄ₓ) that crystallizes in the tetragonal system and occurs chiefly in sandstone-hosted uranium deposits.
- A rare tetragonal uranium silicate mineral, U(SiO₄)₁₋ₓ(OH)₄ₓ, occurring as black, opaque, microcrystalline material in sandstone-type and other low-temperature uranium deposits.
"The drill core revealed fine-grained coffinite coating the quartz grains of the ore zone."
"Petrographic analysis showed coffinite replacing detrital organic matter within the reduced sandstone."
"Alongside pitchblende, coffinite is one of the principal ore minerals mined at several Wyoming basins."
Rarely used; the plural appears only when referring to multiple distinct occurrences, specimens, or varieties of the mineral rather than the substance itself, which is normally treated as uncountable.
"The survey catalogued coffinites from three separate basin deposits."
Yes, there's a radioactive uranium mineral literally named 'coffinite' — it honours American geologist Reuben Clare Coffin, whose surname made the pun irresistible.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of coffinite
Coffinite was named after the American economic geologist Reuben Clare Coffin (1887–1960), who contributed to the study of uranium and other ore deposits. Like most mineral species, it takes the suffix '-ite', derived ultimately from Greek 'lithos' meaning stone, which is standard for naming minerals. The word is therefore eponymous: its only true lexical relative is the surname Coffin itself, which shares Germanic roots with the burial vessel 'coffin'. The mineral was identified and described in the mid-twentieth century during the boom in United States uranium exploration.
How coffinite is actually used
Strictly a technical term used in mineralogy, geology, and uranium exploration; it does not appear in general conversation. Because it names a single mineral species rather than a category, it has no true synonyms. It is always treated as an uncountable or mass noun when referring to the substance, though 'coffinites' may occasionally appear when referring to distinct occurrences or varieties.
Easily confused with coffinite
Uraninite is a uranium oxide (UO₂) and typically forms cubic crystals, whereas coffinite is a uranium silicate that usually occurs as microcrystalline crusts or coatings.
A coffin is a box for burying a dead body, while coffinite is a radioactive mineral — they are linked only by name, since the mineral honours geologist Reuben Clare Coffin.