Vivianita
Vivianita is a mineral with formula Fe²⁺₃(PO₄)₂·8H₂O, in the Fosfatos group. This specimen comes from Cabeça de Cachorro, São Gabriel da Cachoeira, Amazonas, Brasil and joined the Terrium collection in 2025.
Description
Single, acicular, very thin crystal of deep petrol-green colour with bluish reflections visible under raking light. The surface shows well-marked longitudinal striations and an irregular mid-height fracture that imparts a slight twist to the crystal axis.
History of this specimen
Discovered c. 2018. This kind of material reached the market in 2019–2020 in France alongside ludlamite pieces; but the boom was at Tucson 2022.
About Vivianita
Iron phosphate formed by organic decomposition (animal or human). This 'necromineral' is photosensitive: it oxidises and changes from blue to green on exposure.
About the locality
The Cabeça do Cachorro area, in the far north-west of the state of Amazonas, has produced some of the longest and brightest acicular vivianite crystals in South America. It is a remote, hard-to-reach region, with intermittent artisanal mining.
Technical data
- Catalogue No.
- 0025
- Composition
- Fe²⁺₃(PO₄)₂·8H₂O
- Name
- Vivianita
- Group
- Fosfatos
- Category
- Estélites
- Mine
- Cabeça de Cachorro
- District / Municipality
- São Gabriel da Cachoeira
- Province
- Amazonas
- Country
- Brasil
- Size (cm)
- 9.5 x 0.2 x 0.2
- Weight
- 1.7 g
- Acquired
- 2025
- Etymology
- Named in honour of John Henry Vivian (1785–1855), British mineralogist and politician who discovered it in 1817.
- Quality
- Muy buena
- Value trend
- Estable