Hydropascoite
Chemical formula: Ca<sub>3</sub>[V<sup>5+</sup><sub>10</sub>O<sub>28</sub>]·24H<sub>2</sub>O
Hydropascoite is a rare, secondary vanadium mineral, forming orange, water-soluble coatings and efflorescences on rocks.
Properties
- Mohs hardness
- 1
- Luster
- Dull
- Streak
- Light yellow
- Density
- 2.34
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Translucent to opaque
- Crystal system
- Triclinic
Diagnostic features
## Identification The key diagnostic features of hydropascoite are its intense orange color, very low hardness (it is extremely soft), and its reaction to water – it dissolves in it. It occurs as earthy or powdery coatings on uraniferous sandstones. ## Distinguishing from Similar Minerals It can be confused with pascoite, which is its less hydrated form. Pascoite has a similar color but is harder (approx. 2.5 on the Mohs scale) and crystallizes in the monoclinic system. Differentiation without laboratory analysis is difficult and often relies on the humidity conditions in which the specimen was found. Other orange vanadates, such as hewettite, can also be similar, but usually form fibrous aggregates. ## Crystal Forms Hydropascoite crystals are extremely rare and microscopic in size. It usually forms earthy, powdery, porous coatings and efflorescences on rock surfaces.
Geological environment
## Genesis Hydropascoite is a secondary mineral, forming in the oxidation zones of uranium-vanadium deposits. It forms as a result of weathering and alteration of primary uranium and vanadium minerals (such as montroseite) under low-temperature conditions and the influence of groundwater. It is a typical desert mineral, crystallizing as efflorescences on mine walls and rock outcrops. ## Mineral Associations It co-occurs with other secondary vanadium and uranium minerals, such as pascoite (into which it can transform), hewettite, metahewettite, sherwoodite, as well as gypsum and calcite. ## Localities The most important and classic localities for this mineral are in the USA, in the Colorado Plateau region, particularly in Montrose County (Colorado) and San Juan County (Utah). It is known from many uranium and vanadium mines in this region, such as the mines in Paradox Valley and Gypsum Valley.
Rarity
Very rare
For collectors
## Quality Criteria For collectors, the intensity and uniformity of the orange color are most important. Specimens where hydropascoite forms a thick, rich layer on a small fragment of host rock, creating an aesthetic contrast, are most valued. Due to the microscopic size of the crystals, their form is not a key criterion. Association with other rare vanadates is also important. ## Popular Localities The vast majority of the best collector specimens come from historical and active uranium and vanadium mines in the states of Utah and Colorado in the USA. Specimens from these classic localities are most sought after by collectors specializing in systematic minerals.
Care and storage
## Cleaning This mineral is water-soluble, therefore **it must not be cleaned wet**. Any contact with water, even a damp cloth, will cause damage or complete dissolution. Cleaning can only be done dry, using a very soft brush or carefully blowing off dust with compressed air from a distance. ## What to Avoid Water, acids, bases, and all other chemicals must be strictly avoided. The mineral is very sensitive to changes in humidity – in dry air, it can dehydrate and transform into pascoite. It should be protected from direct sunlight, which can cause fading, and from high temperatures. ## Storage Hydropascoite specimens must be stored in sealed, transparent containers (e.g., "membrane boxes" or boxes with cotton) to protect them from mechanical damage and humidity changes. Store in stable conditions, away from heat and light sources.