Terlinguacreekite
Chemical formula: Hg<sup>2+</sup><sub>3</sub>O<sub>2</sub>Cl<sub>2</sub>
Terlinguacreekite is an extremely rare mercury oxychloride, forming microscopic, yellow coatings and aggregates in the Terlingua area of Texas.
Description
## Characteristics Terlinguacreekite is a secondary mercury mineral, most commonly occurring as earthy or powdery coatings and brittle crusts on host rocks. It forms microscopic, poorly developed crystals that are rarely visible to the naked eye. It is usually observed as clusters and aggregates of an intense yellow color, sometimes with a brownish or reddish tint. ## Physical Properties This mineral is characterized by a very high density, approximately 9.75 g/cm³, which is typical for mercury minerals. The luster is described as adamantine on rare crystal faces, and earthy or dull in the case of aggregates. It is translucent to opaque. Its hardness has not been precisely determined due to the small size and fragility of the crystals. ## Colors and Varieties The predominant color of terlinguacreekite is light yellow to yellowish-brown or yellowish-orange. No color or commercial varieties are distinguished. ## History and Name The mineral's name comes from its discovery locality – Terlingua Creek in Brewster County, Texas, USA. It was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 1982. The type locality is at the Mariposa Mine (Perry Pit) in the famous Terlingua mercury district. ## Uses Due to its extreme rarity and toxicity, terlinguacreekite has no industrial applications. It is of scientific interest only and is a prized acquisition in advanced collections of rare minerals and micromounts.
Diagnostic features
## Identification Features facilitating identification include: intense yellow color, occurrence as coatings and crusts, very high density, and co-occurrence with other rare mercury minerals. Its origin from the Terlingua district in Texas is also characteristic. However, definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis. ## Distinguishing from Similar Minerals Terlinguacreekite can be confused with other secondary, yellow mercury minerals from the same locality, such as montroydite (HgO) or terlinguaite (Hg₂OCl). Montroydite usually has a more orange or reddish hue. Terlinguaite is also yellow, but often reacts to UV light and darkens over time. Final distinction of these minerals in microscopic aggregates is almost exclusively possible through laboratory analysis. ## Crystal Forms Crystals are microscopic, poorly formed, tabular or bladed. Most often, it forms earthy, powdery, or dusty aggregates, coatings, and thin crusts.
Geological environment
## Genesis Terlinguacreekite is a secondary mineral, formed in the oxidation zone of mercury deposits. It forms as a result of weathering processes and transformations of earlier mercury minerals, mainly native mercury and calomel, under low-temperature conditions. It occurs in voids and fractures of weathered carbonate rocks (limestones) and clays. ## Mineral Associations This mineral co-occurs with a whole range of other, often rare, mercury minerals. Its typical associations include: calomel (Hg₂Cl₂), native mercury (Hg), terlinguaite (Hg₂OCl), montroydite (HgO), eglestonite (Hg₄OCl₂), as well as calcite and gypsum. ## Localities This is a mineral with extremely limited occurrence. The vast majority, if not all, known specimens come from one location in the world – the Terlingua mining district in Brewster County, Texas, USA. The most important locality there is the Mariposa Mine (also known as Perry Pit).
Rarity
Extremely rare
Collector aspects
## Quality Criteria The collector's value of terlinguacreekite specimens depends on several factors. Highly prized are rich, intensely colored coatings on the smallest possible rock matrix. An additional advantage is the presence of well-defined (though still microscopic) crystals and co-occurrence with other rare mercury minerals, especially if they form aesthetic associations. Due to the nature of the mineral, almost all specimens on the market are micromounts. ## Popular Localities The only source of collector specimens is the historic Terlingua mercury district in Texas. Specimens from this locality, especially from the Mariposa Mine, are considered classic and most desired by collectors specializing in rare minerals or minerals from specific localities (so-called "type locality specimens").
Care and storage
## Cleaning Terlinguacreekite specimens are extremely delicate and toxic. They should absolutely not be cleaned with water or any chemicals. Dust can only be removed with a very gentle stream of air (e.g., from a rubber photographic blower). Any mechanical contact risks damaging the coating. ## What to Avoid **The mineral is highly toxic due to its high mercury content.** Avoid skin contact, and especially inhaling dust. Wash hands thoroughly after any contact with a specimen. Do not heat it, as it releases toxic mercury vapors. Protect it from vibrations, impacts, and abrasion. ## Storage Terlinguacreekite must be stored in a sealed, transparent container (e.g., a "micromount box") to protect it from damage and the release of toxic dust. The container should be clearly labeled with the mineral name and a toxicity warning. Store at a stable temperature, away from direct sunlight, in a place inaccessible to children and pets.