Holdenite

Chemical formula: Mn<sup>2+</sup><sub>6</sub>Zn<sup>2+</sup><sub>3</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>(SiO<sub>4</sub>)(OH)<sub>8</sub>

Holdenite is a rare manganese and zinc arsenate and silicate, forming small, pink to reddish-pink crystals with a vitreous luster.

## Characteristics Holdenite is a complex manganese and zinc arsenate and silicate. It occurs as small, elongated or tabular crystals, rarely exceeding a few millimeters in length. It typically forms radial aggregates or rosettes, and also appears as granular masses filling small fissures in the host rock. Its characteristic color and mode of occurrence make it recognizable, despite the small size of its crystals. ## Physical Properties Holdenite crystals exhibit a vitreous luster. The mineral is translucent. Its Mohs hardness is approximately 4. It is relatively brittle, as evidenced by its uneven fracture. ## Colors and Varieties Holdenite is characterized by a pink to reddish-pink color, sometimes with a violet tint. The streak is pale pink. No color varieties or commercial varieties have been distinguished. ## History and Name The mineral was discovered at the Franklin Mine in Sussex County, New Jersey (USA). It was described by Charles Palache, Lawson H. Bauer, and Harry Berman in 1927. The name holdenite was given in honor of Albert Fairchild Holden (1866-1913), a mining engineer and avid mineral collector, whose collection became the foundation of the Harvard University mineralogical collections.

Properties

Mohs hardness
4
Luster
Vitreous
Streak
Pale pink
Density
4.12
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Diagnostic features of holdenite include its characteristic pink to reddish-pink color, radial aggregates of small, elongated crystals, and association with minerals from Franklin. The pale pink streak is also helpful in identification. ## Distinguishing from Similar Minerals Holdenite can be confused with other pink minerals from Franklin, such as rhodonite or pyrochroite. It differs from them in crystal habit (elongated, in radial aggregates), lower hardness, and specific chemical composition, which requires advanced analysis for confirmation. ## Crystal Forms Holdenite crystals are typically elongated along the crystallographic a-axis, often flattened, with a tabular habit. They form characteristic radial aggregates, rosettes, and fibrous or acicular groupings. They also occur as granular masses.

Geological environment

## Genesis Holdenite is a mineral of metamorphic origin. It formed as a result of the metamorphism of zinc and manganese ore deposits. It occurs in calcite veins cutting franklinite-willemite ores. ## Mineral Associations This mineral co-occurs with many other minerals from the Franklin deposit, such as willemite, franklinite, zincite, calcite, as well as rarer species like flinkite, allactite, pyrochroite, magnussonite, and kotoite. ## Localities The only confirmed and classic locality for holdenite in the world is the Franklin Mine in Sussex County, New Jersey, USA. This is the type locality for this mineral.

Rarity

Very rare

For collectors

## Quality Criteria The most valuable holdenite specimens are those with well-formed, macroscopically visible crystals of intense pink color, forming aesthetic, radial aggregates on a contrasting rock matrix. Due to the small size of the crystals, specimens with distinct, large (over a few millimeters) crystals are exceptionally prized. ## Popular Localities The only source of holdenite specimens is the historic Franklin Mine in New Jersey. All specimens available on the collector's market come from this single location and are material from old collections.

Care and storage

## Cleaning Due to its rarity and brittleness, mechanical cleaning is not recommended. If necessary, compressed air can be used to remove loose dust particles. Contact with water should be kept to a minimum. ## What to Avoid Contact with acids, which can damage the mineral, must be strictly avoided. Holdenite is brittle, so it should be protected from impacts and vibrations. It should not be heated or subjected to ultrasonic cleaning. ## Storage Holdenite specimens are best stored in their original host rock, in sealed collector boxes that protect against dust and mechanical damage. Exposure to humid environments should be avoided.

Sources

Read more