Phosphorrösslerite
Chemical formula: Mg(PO<sub>3</sub>OH)·7H<sub>2</sub>O
Phosphorrösslerite is a hydrated magnesium phosphate, forming colorless, acicular crystals, found in caves with bat guano.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous
- Streak
- White
- Density
- 1.705
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Phosphorrösslerite is identified based on its specific environment of occurrence (caves with guano), form (fine, acicular crystals in aggregates), and physical properties – it is very soft and light. The lack of color and vitreous luster are also characteristic. ## Distinguishing from similar minerals It can be confused with other secondary phosphate or sulfate minerals found in caves, such as gypsum or newberyite. It differs from gypsum by its crystal form (gypsum rarely forms such fine needles). From newberyite, with which it often co-occurs, it can be difficult to distinguish without advanced studies (e.g., XRD). ## Crystal forms It forms elongated, acicular or fibrous crystals, often grouped into radial aggregates, rosettes, bundles, or forming crusty coatings on rocks.
Geological environment
## Genesis This is a secondary mineral, formed under specific conditions. It forms as a result of the reaction of solutions rich in phosphoric acid, derived from the decomposition of bat guano, with magnesium-rich carbonate rocks (dolomites, dolomitic limestones) or serpentinites, on which the guano lies. ## Mineral associations It most often co-occurs with other phosphates formed under similar conditions, such as newberyite, struvite, hannayite, as well as with gypsum, calcite, and dolomite. ## Localities The most important occurrences of this mineral are associated with caves. It is known from the "Drachenhöhle" cave in Mixnitz, Austria (type locality), from the "Pig Hole" cave in Giles County, Virginia (USA), and from caves on the Eyre Peninsula in South Australia.
Rarity
Rare
For collectors
## Quality criteria The most prized specimens are those with well-formed, naked-eye visible acicular crystals forming rich, radial aggregates or dense coatings on a small rock matrix. Contrast with a darker host rock enhances visual appeal. Due to its brittleness, undamaged specimens collected are rare. ## Popular localities Classic and most valued specimens come from the type locality in Mixnitz, Austria. High-quality material is also provided by localities in South Australia (e.g., Wooltana Cave).
Care and storage
## Cleaning Phosphorrösslerite specimens are extremely delicate and sensitive to water. Mechanical cleaning is inadvisable. If necessary, a stream of compressed air from a distance can be used to remove loose dust. ## What to avoid Contact with water, which can dissolve or damage the mineral, must be strictly avoided. It should be protected from high temperatures, which can cause dehydration and destruction of the crystals. Avoid all chemicals and ultrasonics. The mineral is very brittle, so shocks and touching should be avoided. ## Storage Specimens should be stored in closed, airtight containers (e.g., "membrane box" type or in boxes away from dust and humidity), at a stable room temperature. Due to its brittleness, it should not be stored in contact with harder minerals.