Goethite?

Field of view: 5 mm. The acicular yellow crystals are probably goethite. The surrounding reniform pale blue groups are chalcoalumite. The brown grains encrusted with chalcoalumite are siderite.

Recovered from an open space of a quartz vein in a meteoric oxidation zone of a moderate-temperature hydrothermal deposit associated with rhyolite.

Goethite from this location was described in 1961.