Windmountainite

windmountainite

fluorapophyllite-(K)

montmorillonite

neotocite

Images

Formula: ☐Fe³⁺₂Mg₂☐₂Si₈O₂₀(OH)₂.8H₂O
Phyllosilicate, palygorskite group
Crystal System: Monoclinic
Specific gravity: 2.51 calculated
Hardness: 2
Streak: Orange-brown
Colour: Orange-brown
Environments

Igneous environments

Windmountainite is a new mineral species, approved in 2019.

Localities

At the type locality, Wind Mountain, Cornudas Mountains, Otero county, New Mexico, USA, windmountainite was discovered as orange-brown, radiating aggregates that commonly fill vesicles within a phonolite dike as tightly bound bundles of acicular to bladed crystals.
Associated minerals include albite, aegirine, fluorapophyllite-(K), natrolite, neotocite and montmorillonite, the last of these being observed to replace primary windmountainite.
Windmountainite is considered to have formed from late-stage fluids that were alkaline and oxidised, in conditions reflective of abundant, hydrated feldspathoids (natrolite and analcime) forming as primary rock-forming minerals in the phonolite at Wind Mountain (CM 58.477-509).

Windmountainite from Wind Mountain - Image

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