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.
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
- 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