Dendoraite-(NH_4_)

Chemical formula: (N<sup>3-</sup>H<sub>4</sub>)<sub>2</sub>NaAl((C<sub>2</sub>)<sup>6+</sup>O<sub>4</sub>)(PO<sub>3</sub>OH)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>

Dendoraite-(NH₄) is an extremely rare phosphate mineral, found in caves as microscopic, colorless crystals.

## Characteristics Dendoraite-(NH₄) is a hydrated aluminum, sodium, and ammonium phosphate with an additional oxalate group. It forms extremely small, bladed or acicular crystals, typically not exceeding 0.2 mm in length. They are colorless and transparent, with a vitreous luster. Due to their microscopic size, their visual features are only discernible under high magnification. ## Physical properties The crystals are very brittle. Hardness and density have not been precisely measured due to the small quantity and size of the material. The calculated density is approximately 2.18 g/cm³. ## Colors and varieties The mineral is colorless. No varieties are known. ## History and name The mineral's name refers to the Dhenda (or Denda) Cave in Israel, where it was discovered, and to the dominant ammonium cation (NH₄) in its composition. It was approved by the International Mineralogical Association (IMA) in 2023 (IMA 2023-091). It was described by a team of mineralogists led by Sergey N. Britvin. ## Applications Due to its extreme rarity and microscopic size, Dendoraite-(NH₄) has no practical applications. It is solely an object of scientific and collecting interest for specialized micromineral collectors.

Properties

Luster
Vitreous
Streak
White
Density
2.18
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of Dendoraite-(NH₄) is impossible without advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), due to its microscopic size and lack of characteristic visual features visible to the naked eye. It is distinguished by colorless, bladed crystals with a vitreous luster. ## Distinguishing from similar minerals It co-occurs with other rare phosphates and oxalates, from which it is practically impossible to distinguish visually. Certain differentiation requires chemical and structural analysis. ## Crystal forms It forms elongated, bladed or acicular crystals, often grouped into small, radial aggregates or chaotic clusters on the surface of the host rock.

Geological environment

## Genesis Dendoraite-(NH₄) is a biogenic mineral, formed under specific conditions prevailing in caves. Its formation is associated with reactions between solutions rich in phosphates and ammonia, originating from the decomposition of bat guano, and clay minerals containing aluminum, which form the cave walls. ## Mineral associations It co-occurs with other rare cave minerals such as spheniscidite, newberyite, taranakite, variscite, as well as gypsum and quartz. ## Localities The only confirmed occurrence of this mineral in the world is its type locality - Dhenda (Denda) Cave in the Judean Desert, Israel.

Rarity

Extremely rare

For collectors

## Quality criteria For micromineral collectors, the most important aspect is the presence of well-formed, sharp, and undamaged crystals, even if they are microscopic. Specimens where crystals form aesthetic, rich groups or are clearly isolated on a contrasting host rock background are highly valued. Due to its extreme rarity, any specimen containing confirmed Dendoraite-(NH₄) is considered extremely valuable. ## Popular localities The only source of specimens is Dhenda Cave in Israel, which makes them practically unavailable on the commercial market. Specimens are mainly found in institutional collections and among specialized collectors who acquired them for research purposes.

Care and storage

## Cleaning Specimens of this mineral should not be cleaned mechanically or chemically. Any attempts at cleaning will almost certainly destroy the delicate, microscopic crystals. They should be left undisturbed on the host rock. ## What to avoid Avoid contact with water and chemicals that can dissolve the mineral. The crystals are extremely brittle, so avoid any vibrations, shocks, and touching. Protect it from changes in temperature and humidity. ## Storage Specimens should be stored exclusively in specialized micromount boxes, which protect them from dust, mechanical damage, and humidity changes. Display is only possible under a microscope.

Sources

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