Cumengeite, also known as cumengite, is a secondary mineral that was named after mining engineer Bernard Louis Philippe Édouard Cumenge, who found the first specimens. It is easily confused with diaboleite. It is a valid species that was first described prior to 1959, and is grandfathered now, but it has been a valid species since 1893, since pre-IMA. It is the hydroxychloride of lead and copper.
{{Infobox mineral |boxbgcolor=#4757f6 |boxtextcolor = #fff |image=Cumengeite-266101.jpg |formula=Pb21Cu20Cl42(OH)40 · 6H2O |IMAsymbol=Cge |strunz=3.DB.20 |system=Tetragonal |dana=10.6.7.1 |class=Ditetragonal Dipyramidal H-M Symbol: 4/mmm (4/m 2/m 2/m) |symmetry=I4/mmm |unit cell=5,545.85 |color=Indigo blue |cleavage=Good on {101} Distinct on {110} Poor on {001} |mohs=2.5 |luster=Sub-vitreous |opticalprop=Uniaxial (−) |refractive=nω = 2.026 – 2.041 nε = 1.926 – 1.965 |birefringence=0.100 |pleochroism=Visible |streak=Sky-blue |gravity=4.656 |density=Measured: 4.656 Calculated: 4.66 |solubility=Soluble in HNO3 |diaphaneity=Translucent}}
Cumengeite, also known as cumengite, is a secondary mineral that was named after mining engineer Bernard Louis Philippe Édouard Cumenge, who found the first specimens. It is easily confused with diaboleite. It is a valid species that was first described prior to 1959, and is grandfathered now, but it has been a valid species since 1893, since pre-IMA. It is the hydroxychloride of lead and copper.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).