Philipsburgite

Chemical formula: Cu₂+₅Zn₂+(As₅+O₄)(PO₄)(OH)₆·H₂O

Philipsburgite is a rare copper and zinc arsenate and phosphate, forming characteristic green, spherical aggregates.

## Characteristics Philipsburgite is a hydrated copper and zinc arsenate and phosphate. It most commonly occurs as spherical or hemispherical aggregates with a radial, fibrous internal structure. It also forms crusts and coatings. Individual crystals are very small, acicular or platy, and rarely visible to the naked eye. Its structure is closely related to kipushite. ## Physical Properties This mineral is characterized by a vitreous luster. It is translucent to opaque. Its Mohs hardness is approximately 3, and its density ranges from 4.05 to 4.13 g/cm³. ## Colors and Varieties Philipsburgite has a characteristic, vivid, emerald-green or dark green color. No color or commercial varieties are distinguished. ## History and Name The mineral's name comes from its discovery locality – the Black Pine Mine near Philipsburg in Granite County, Montana, USA. It was described and approved as a new mineral species by the International Mineralogical Association (IMA) in 1985. ## Uses Due to its rarity and occurrence in small quantities, philipsburgite has no industrial application. It is of scientific and collector's interest only.

Properties

Mohs hardness: 3
Luster: Vitreous
Streak: Light green
Density: 4.05-4.13
Cleavage: Good on {001}
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Key diagnostic features of philipsburgite include its intense green color, spherical or radial aggregates, and occurrence in the oxidation zones of ore deposits. Its streak – light green – is also characteristic. ## Distinguishing from Similar Minerals Philipsburgite can be confused with other secondary copper minerals, such as malachite, pseudomalachite, brochantite, or kipushite. It differs from malachite by its lack of reaction with hydrochloric acid (malachite effervesces). Distinguishing it from pseudomalachite and kipushite often requires advanced chemical (EDS) or X-ray (XRD) analyses for unambiguous identification. However, its radial aggregates are quite characteristic. ## Crystal Forms Crystals are very fine, acicular or platy, elongated along the [010] axis and flattened parallel to {001}. Most commonly, they form spherical, radially fibrous aggregates, as well as crusts.

Geological environment

## Genesis Philipsburgite is a secondary mineral, forming in the oxidation (weathering) zones of polymetallic ore deposits rich in copper, zinc, and arsenic. It forms as a result of surface waters acting on primary ore minerals, such as chalcopyrite, sphalerite, and tennantite. ## Mineral Associations It often co-occurs with other secondary minerals, such as quartz, goethite, pseudomalachite, kipushite, agardite, olivenite, mimetite, cerussite, and anglesite. ## Localities The most important and type locality is the Black Pine Mine near Philipsburg, Montana, USA. It is also known from several other localities worldwide, including the Clara Mine in the Black Forest (Germany), the Tsumeb Mine (Namibia), and small occurrences in Cornwall (United Kingdom).

Rarity

Rare

For collectors

## Quality Criteria Most valued by collectors are specimens with well-formed, spherical aggregates of intense, emerald-green color. Contrast with the rock matrix (most often quartz or goethite) and the absence of damage to the delicate, spherical forms are important. The size of the aggregates also affects value – larger and more distinct spheres are more desirable. ## Popular Localities Undoubtedly, the most sought-after and classic specimens come from the type locality – the Black Pine Mine in Montana, USA. Specimens from the Clara Mine in Germany are also prized in specialized collections.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Contact with water should be kept to a minimum; if necessary, use distilled water and immediately dry the specimen thoroughly with cool air. Due to its arsenic content, avoid inhaling dust and wash hands after contact with the mineral. ## What to Avoid Avoid all chemicals, especially acids, which can rapidly destroy the mineral. Do not heat it or expose it to prolonged strong light. It is brittle and sensitive to ultrasound. ## Storage It is recommended to store specimens in closed, stable containers or display cases, away from dust, moisture, and direct sunlight. Protect it from impacts and vibrations.

Sources

IMA Mineral List (CNMNC)