Yeatmanite

Properties

Mohs hardness

4

Luster

Resinous to Sub-Metallic

Streak

Brown

Density

5.02

Cleavage

Perfect on {001}

Fracture

Uneven

Transparency

Opaque

Crystal system

Triclinic

Diagnostic features

## Identification Amateur identification of yeatmanite is practically impossible. It requires advanced analytical techniques such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). In a collection, it can be identified based on the label and confirmed locality (Franklin, New Jersey). Visual characteristics such as dark brown color, resinous luster, and tabular crystal habit are only indications. ## Distinguishing from Similar Minerals Yeatmanite co-occurs with many other rare minerals from Franklin, such as franklinite, willemite, and zincite. Visually, it may resemble small crystals of franklinite or other dark oxide minerals. Definitive differentiation is only possible using laboratory methods. ## Crystal Forms Yeatmanite crystallizes in the trigonal system. It forms very small, thin, tabular crystals, often with hexagonal or rhombic outlines. These crystals rarely occur individually, usually forming small clusters and aggregates on the surface of other minerals.

Geological environment

## Genesis Yeatmanite is a product of contact metamorphism acting on zinc, iron, and manganese ore deposits. It forms under specific geochemical conditions characteristic of the Franklin deposit in New Jersey. It is a secondary mineral, forming in fractures and voids within zinc ores. ## Mineral Associations This mineral occurs in association with other, often rare, minerals typical of the Franklin locality. It most commonly co-occurs with willemite, franklinite, zincite, friedelite, andradite, and calcite. ## Localities The only confirmed occurrence of yeatmanite in the world is the Franklin Mine, Sussex County, New Jersey, USA. This is its "type locality" – the place from which the mineral was first described.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a yeatmanite specimen is primarily determined by the abundance and development of its crystals. The most prized specimens are those that display numerous, well-formed, albeit microscopic, tabular crystals with a distinct luster. Contrast with the host rock (matrix), for example with white calcite, also enhances the visual appeal of the specimen. The size of individual crystals, even if exceeding 1 mm, is considered exceptional. ## Popular Localities The only source of yeatmanite specimens is the historic Franklin Mine in New Jersey, USA. All specimens available on the collector's market originate from this single locality, making them extremely desirable for collectors specializing in minerals from this location and for rare minerals (so-called "micromounts").

Care and storage

## Cleaning Yeatmanite specimens are extremely delicate and small, so intense mechanical cleaning should be avoided. The safest method is to use compressed air to remove dust. If wet cleaning is necessary, only distilled water and a very soft brush should be used, applied with utmost care. ## What to Avoid Contact with acids and other chemicals that can damage the mineral must be strictly avoided. Yeatmanite is brittle, so it should be protected from impacts, scratches, and vibrations. It should not be heated or subjected to ultrasound. ## Storage Yeatmanite specimens, due to their microscopic size and fragility, should be stored in specialized, sealed "micromount" boxes. This protects them from dust, mechanical damage, and loss. Exposure to direct sunlight should be avoided, although it is not considered particularly harmful.

Sources

• IMA Mineral List (CNMNC)