Hummerite
Chemical formula: K₂Mg₂[V⁵⁺₁₀O₂₈]·16H₂O
Hummerite is a rare, orange-red vanadate mineral, forming aggregates of fine crystals and coatings on host rocks.
Properties
- Mohs hardness
- 2.5
- Color
- Bright orange, yellow
- Luster
- Vitreous to resinous
- Streak
- Orange-yellow
- Density
- 0
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification Hummerite is primarily identified by its intense orange-red color, characteristic aggregates of fine, tabular crystals, and its occurrence in paragenesis with other vanadium minerals. A key diagnostic feature is its water solubility, which, however, is a destructive test. ## Distinguishing from Similar Minerals It can be confused with other secondary vanadium minerals of similar color, such as pascoite or hewettite. Pascoite crystallizes in the monoclinic system and has a slightly different hue. Hewettite is also monoclinic and often forms acicular or fibrous aggregates. Accurate distinction of these minerals without advanced studies (e.g., XRD) is very difficult and relies mainly on the analysis of crystal habit and paragenesis. ## Crystal Forms Hummerite crystals are small, tabular or bladed, elongated along one axis. They usually form granular aggregates, rosettes, radial aggregates, or occur as coatings and efflorescences on rocks, most commonly sandstones.
Geological environment
## Genesis Hummerite is a secondary mineral, forming in the oxidation zone of uranium-vanadium deposits found in sedimentary rocks, mainly sandstones. It forms as a result of weathering and alteration of primary vanadium minerals (e.g., montroseite) under desert and semi-desert conditions. Its formation is associated with the activity of groundwater rich in dissolved vanadates. ## Mineral Associations This mineral co-occurs with other secondary vanadium and uranium minerals. The most common associated minerals include pascoite, hewettite, sherwoodite, montroseite, as well as gypsum and calcite. ## Localities The most important and classic hummerite localities are in the USA, in the Colorado Plateau region, especially in Montrose County (Colorado) and San Juan County (Utah). It is known from many uranium and vanadium mines in this region, such as the Hummer Mine (type locality), Burro Mine, and Vanadium Queen Mine.
Rarity
Rare
For collectors
## Quality Criteria Specimens with well-formed, distinct crystals of intense, orange-red color are most valued by collectors. Rich crystalline aggregates covering a significant area of the rock matrix are highly prized. Contrast with light sandstone enhances the visual appeal of the specimen. Association with other rare vanadate minerals is also important. ## Popular Localities The best and most sought-after hummerite specimens come from classic localities in the USA, particularly from mines in Paradox Valley and surrounding areas (Montrose County, Colorado) and the La Sal region (San Juan County, Utah). Specimens from these locations are considered the global standard for this mineral.
Care and storage
## Cleaning Hummerite specimens should be cleaned only with extreme care, using a soft brush to remove dust. The mineral is water-soluble, so contact with water and other liquids must be strictly avoided. Wet cleaning will lead to its destruction. ## What to Avoid Avoid contact with water, acids, bases, and all chemical agents. The mineral is sensitive to moisture, which can cause its disintegration. It should also be protected from high temperatures, which can lead to dehydration and structural changes. Avoid abrasion and impacts due to its low hardness. ## Storage Hummerite specimens should be stored in a dry place, preferably in a sealed, airtight container (e.g., a "membrane box") with a desiccant (silica gel). It should be protected from direct sunlight and dust. Due to its fragility, it should not be stored in contact with harder minerals.