Holdawayite

Chemical formula: Mn²⁺₆(CO₃)₂(OH)₇(Cl,OH)

Holdawayite is a rare, hydrated manganese carbonate with a characteristic, light pink color, found as small, radial aggregates.

## Characteristics Holdawayite is a rare mineral from the carbonate group, chemically classified as a basic manganese carbonate with chlorine. It most often occurs in the form of small, radially fibrous or spherulitic (spherical) aggregates. Individual crystals are usually very small, bladed or acicular, forming compact masses. Its most characteristic visual feature is a delicate, light to intensely pink color. ## Physical Properties This mineral is characterized by low hardness, 3 on the Mohs scale, which makes it susceptible to scratching. Its density is approximately 3.19 g/cm³. Crystals exhibit a vitreous luster and are translucent. It has one direction of cleavage. ## Colors and Varieties Holdawayite occurs in shades from light to vivid pink. Its color is directly related to the presence of manganese in its chemical structure. No named varieties are distinguished. ## History and Name The mineral was discovered and described in 1986. Its name honors Michael J. Holdaway (1936–2023), an American petrologist and mineralogist from Southern Methodist University, for his contributions to the study of manganese minerals. ## Uses Due to its extreme rarity and small size of occurrences, holdawayite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals or minerals from specific localities.

Properties

Mohs hardness
3
Luster
Vitreous
Streak
Light pink
Density
3.19
Cleavage
{100}
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Diagnostic features of holdawayite include its characteristic pink color, occurrence in the form of radial or spherulitic aggregates, and low hardness (3 on the Mohs scale). It reacts with acids, which is typical for carbonates. The streak is light pink. ## Distinguishing from Similar Minerals Holdawayite can be confused with other pink manganese minerals, such as rhodochrosite or kutnohorite. However, its mode of occurrence distinguishes it – rhodochrosite rarely forms fibrous aggregates, more often rhombohedral crystals or massive and banded aggregates. Kutnohorite can be similar, but definitive differentiation requires advanced chemical analyses (EDS/XRD). ## Crystal Forms It forms elongated, bladed crystals, which most often arrange into radial, fibrous, or spherical aggregates (spherulites). Single, well-formed crystals are extremely rare.

Geological environment

## Genesis Holdawayite is a secondary mineral, forming in the oxidation zones of manganese ore deposits. It forms as a result of the alteration of primary manganese minerals under low temperature and pressure conditions, in the presence of carbonate and chloride-rich solutions. ## Mineral Associations This mineral co-occurs with other secondary manganese minerals. In the type locality (Kombat Mine), it was found in association with minerals such as: barite, hausmannite, pyrochroite, kutnohorite, as well as rare species like queitite and kombatite. ## Localities The most important and also the type locality for holdawayite is the Kombat Mine in the Otjozondjupa region of Namibia. This is the only locality from which well-documented, classic specimens of this mineral originate.

Rarity

Very rare

For collectors

## Quality Criteria The most highly prized holdawayite specimens are those that exhibit an intense, vivid pink color and well-formed, spherical or radial aggregates. The aesthetics of the composition are also important – specimens where pink spherulites contrast with a darker matrix rock are attractive. Due to its rarity, every specimen, even a small one, is considered valuable. ## Popular Localities The only source of collector specimens is the Kombat Mine in Namibia. Material from this locality is the standard for this mineral, and practically all specimens available on the market come from there.

Care and storage

## Cleaning Holdawayite specimens should be cleaned with the utmost care, using only a soft brush to remove dust. Due to its low hardness and reactivity, contact with water, and especially with acids, should be avoided. ## What to Avoid All chemicals, including acids (even weak ones like vinegar), which can react violently with carbonates, must be strictly avoided. The mineral is soft and brittle, so it must be protected from impacts, scratching, and vibrations. It should not be heated or exposed to prolonged moisture. ## Storage It is recommended to store specimens in stable conditions, in a closed display box, away from dust, moisture, and direct sunlight. It is best to isolate it from harder minerals to avoid accidental damage.

External references

Sources

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