Coquimbite
3 in the gallery
Coquimbite is a hydrated ferric aluminum sulfate mineral in the sulfate family. It typically forms as colorless to yellow, gray, or pinkish crystals that can be transparent to translucent, with a vitreous luster and a prismatic, tabular, or granular habit. It is notably unstable, often converting to other hydrated sulfates when exposed to drying or heat, which influences how specimens are collected and stored. Specimens commonly show perfect cleavage and a conchoidal to uneven fracture, with a relatively low hardness around 2 to 2.5 on the Mohs scale, and a modest specific gravity near 2.1. Chrome‑bright or pale tints can appear due to trace impurities, and crystals may be relatively small but can form aggregates or granular masses.
- Formula
- AlFe₃(SO₄)₆(H₂O)₁₂·6H₂O
- Rarity
- Uncommon
- Stability
- Unstable
- Collector interest
- Moderate Interest
- Classification notes
- Sulfates; hydrated ferric aluminum sulfate mineral
Key characteristics
- Crystal system
- trigonal
- Mohs hardness
- 2–2.5
- Specific gravity
- 2.09–2.17
- Luster
- vitreous
- Transparency
- transparent, translucent
- Color
- colorless, white, gray, yellow, green, blue, violet, pink
- Streak
- white
- Cleavage
- perfect
- Fracture
- conchoidal, uneven
- Crystal habit
- prismatic, tabular, granular, massive
Where Coquimbite is found
Top localities
- Javier Mine1 specimen
About Coquimbite
Specimens sourced from Peru and Spain are well regarded by collectors for their rare occurrence and the mineral’s delicate, glassy appearance. Mineral enthusiasts value coquimbite for its vivid potential color range when the composition includes subtle variations, and for its association with layered sulfate assemblages found in arid volcanic or hydrothermal settings. The combination of its striking mineral beauty, fragility, and relatively limited yet steady availability makes coquimbite a desirable, if carefully stored, addition to a polished cabinet or display, where it can be appreciated without risking rapid dehydration or alteration.