Arseniosiderite
5 in the gallery
Arseniosiderite is a calcium iron arsenate mineral that forms as small, typically slender crystals or a tabular habit with a vitreous to resinous luster. It often appears in pale orange to brown hues and can occur as well-formed crystals on host rocks or in crust-like aggregates, giving it a delicate yet striking presence on specimen cabinets.
- Formula
- Ca2Fe3+3(AsO4)3O2·3H2O
- Rarity
- Uncommon
- Stability
- Stable
- Collector interest
- Niche Interest
- Classification notes
- Arsenate; mitridatite group; Strunz 8.DH
Key characteristics
- Crystal system
- monoclinic
- Mohs hardness
- 4.5
- Specific gravity
- 3.5–3.6
- Luster
- vitreous, silky, dull
- Transparency
- translucent, opaque
- Color
- brown, yellow, red, black
- Streak
- brown, yellow
- Cleavage
- none
- Fracture
- uneven
- Crystal habit
- fibrous, radiating, botryoidal, massive
Where Arseniosiderite is found
Top localities
- Christiana Mine1 specimen
- Ojuela Mine1 specimen
About Arseniosiderite
Notable localities for arseniosiderite include diverse locales such as Mexico, France, Namibia, and the United States, where specimens have been described by mineral collectors for generations. The mineral’s rarity and the specific geological settings required for its formation contribute to its status as a niche-interest piece, appreciated for its unique composition and the challenge of locating well-formed examples. Collectors value arseniosiderite for the combination of color, crystal habit, and the story of its formation in carbonate-rich and arsenic-bearing environments, where it can present as bright, translucent crystals or subtle, earthy aggregates.