Packratite

Chemical formula: Ca₁₁(As₃+V₅+₁₀V₄+₂As₅+₆O₅₁)₂·₈₃H₂O

An extremely rare, secondary calcium arsenate-vanadate, forming microscopic, acicular yellow crystals.

## Characteristics Packratite is a mineral with an exceptionally complex chemical composition, occurring as brittle crusts and coatings. It forms aggregates of small, acicular or bladed crystals that rarely reach sizes visible to the naked eye. Typical specimens are pale yellow to yellowish-brown and appear as delicate, fluffy or fibrous aggregates on the host rock. Due to the microscopic size of its crystals, it is classified as a typical micromineral. ## Physical Properties This mineral is extremely soft, with a Mohs hardness estimated at approximately 1. It is very light, with a calculated density of about 2.2 g/cm³. The luster is described as vitreous to silky, which is characteristic of its fibrous structure. It is translucent. ## Colors and Varieties Packratite occurs in shades from pale yellow to yellowish-brown. No color varieties or commercial varieties are known. ## History and Name The mineral's name, "packratite", comes from the English name for the packrat (genus *Neotoma*). It was discovered in a fossilized nest (a "packrat midden") at the Carlin-Goldstrike mine in Eureka County, Nevada, USA. It was described in 2016 by a team of mineralogists led by Anthony R. Kampf. Its formation is directly related to the unique chemical environment that developed within this nest. ## Uses Packratite has no commercial or industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare minerals and microminerals.

Properties

Mohs hardness: 1
Luster: Vitreous to Silky
Streak: Pale yellow
Density: 2.2
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Field identification of packratite is impossible. It requires advanced laboratory techniques such as X-ray diffraction (XRD) and chemical analysis (EDS). Preliminary indications may include its unique occurrence environment (packrat middens in Nevada), yellow color, fibrous form, and co-occurrence with other rare arsenates. ## Distinguishing from Similar Minerals It can be confused with many other secondary, yellow minerals, such as pharmacolite, sulfates, or other rare vanadates and arsenates. Definitive differentiation is only possible based on detailed analytical studies. ## Crystal Forms It forms aggregates of microscopic, acicular or bladed crystals. These aggregates take the form of crusts, coatings, and delicate, fibrous masses.

Geological environment

## Genesis Packratite is a secondary mineral of post-mining genesis. It formed as a result of reactions between meteoric waters and ore minerals containing arsenic and vanadium, which were exposed during mining operations. The specific chemical environment of the fossilized packrat midden, rich in organic matter, played a key role in its formation. ## Mineral Associations It co-occurs with other extremely rare secondary minerals discovered in the same locality, such as anarakite, caotheite, chachaite, goldstrikeite, and nevadaite. ## Localities The only known occurrence of this mineral in the world is its type locality: Little-Eva No. 1 Claim, Carlin-Goldstrike Mine, Goldstrike District, Eureka County, Nevada, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, packratite is primarily evaluated based on the quality and richness of crystal aggregates on the rock matrix. The most valuable specimens are those with clearly formed, though still microscopic, crystals, forming dense, fluffy aggregates. Documentation confirming origin from the only known locality is also important. ## Popular Localities The only source of packratite specimens is its discovery site in Nevada, USA. This mineral is not available on the open commercial market and is almost exclusively acquired by research institutions and the most specialized collectors of rare mineral species.

Care and storage

## Cleaning Packratite specimens are extremely delicate and potentially sensitive to moisture. Wet cleaning is absolutely forbidden. If necessary, a very gentle stream of compressed air or a soft, dry brush can be used to remove dust. ## What to Avoid Contact with water, all liquids, and chemicals should be avoided. The mineral is very soft and brittle, susceptible to mechanical damage. Due to the high water content in its crystal structure, high temperatures and sudden changes in humidity should be avoided, as these can lead to its decomposition. ## Storage Specimens should be stored in stable conditions, in a closed, dry container (e.g., a "perky box" used for microminerals). It is recommended to keep it away from direct sunlight and heat sources to prevent degradation.

Sources

IMA Mineral List (CNMNC)