Blue aragonite (probable)

Pale turquoise-blue, vitreous to pearly luster, translucent-to-opaque and commonly fibrous or botryoidal; Mohs hardness 3.5–4, orthorhombic crystal structure, imperfect cleavage, specific gravity about 2.9–3.0. The image supports a blue carbonate mineral identification, but visual identification alone is not definitive.

Forms in low-temperature hydrothermal veins, caves, evaporite settings, and as secondary crusts; copper-bearing varieties commonly form through mineral-rich groundwater alteration. Aragonite is geologically younger and less stable at Earth’s surface than calcite, often recrystallizing over time.

Used mainly as a decorative, lapidary, and collector specimen; rarely used industrially because calcite is the more stable and abundant CaCO₃ polymorph.

It effervesces vigorously with dilute hydrochloric acid or vinegar powder, though acid testing can damage the specimen. Blue aragonite is sometimes confused with turquoise, chrysocolla, or dyed calcite.

Commonly found in Spain, Morocco, Mexico, Namibia, and parts of the southwestern United States; confirm with acid reaction, hardness, streak, and ideally Raman/X-ray testing. Avoid prolonged sunlight, heat, and acids.