Eitelite

Chemical formula: Na<sub>2</sub>Mg(CO<sub>3</sub>)<sub>2</sub>

Eitelite is a rare, colorless or white sodium magnesium carbonate, forming characteristic, sharply terminated rhombohedral crystals.

## Characteristics Eitelite is a rare mineral from the carbonate group, chemically a double carbonate of sodium and magnesium. It typically forms well-developed, single crystals in the shape of flattened or elongated rhombohedra, often with sharp terminations. Crystals can be transparent and colorless, but may also take on shades of white, gray, or yellow. Crystal surfaces are characterized by a vitreous, and sometimes pearly, luster. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 3.5. It has perfect cleavage in three directions, consistent with its rhombohedral form, which makes it brittle. The density of eitelite is approximately 2.66 g/cm³. It is transparent to translucent. ## Colors and Varieties Eitelite is most commonly colorless or white. Specimens with gray, yellowish, or pale green coloration are also found. No named varieties are distinguished. ## History and Name The mineral was discovered in 1954 in drill core samples from the Green River Formation in Sweetwater County, Wyoming, USA. It was named after Wilhelm Eitel (1891-1979), a German physical chemist and director of the Institute for Silicate Research at the University of Toledo (Ohio, USA), for his contributions to carbonate chemistry. ## Uses Eitelite has no industrial application. It is solely a mineral of scientific and collector interest.

Properties

Mohs hardness
3.5
Luster
Vitreous
Streak
White
Density
2.663
Cleavage
Perfect on {10-14}
Fracture
Conchoidal
Transparency
Transparent to translucent
Crystal system
Trigonal

Diagnostic features

## Identification The key diagnostic feature of eitelite is its characteristic crystal shape – sharply terminated, often flattened rhombohedra. It reacts violently with hydrochloric acid, effervescing, which is typical for carbonates. Its relatively low hardness (3.5 on the Mohs scale) and perfect rhombohedral cleavage are also helpful in identification. ## Distinguishing from Similar Minerals Eitelite can be confused with other colorless carbonates, such as calcite or dolomite. It is distinguished from calcite by a slightly different rhombohedral shape (more flattened or acute) and often by its association with other rare evaporite minerals. Dolomite reacts with hydrochloric acid much more slowly (only after pulverization), while eitelite reacts immediately. Occurrence in a specific geological environment (evaporite formations) is also an important clue. ## Crystal Forms Eitelite crystallizes in the trigonal system, forming simple rhombohedra {10-14}. Crystals are often flattened along the crystallographic c-axis or, conversely, elongated along it, giving them a needle-like appearance. More rarely, it occurs in granular aggregates.

Geological environment

## Genesis Eitelite is an authigenic mineral, crystallizing in sodium- and magnesium-rich sediments under high pH conditions. It forms in evaporitic sedimentary rocks, most often in shales and siltstones of lacustrine formations that have undergone desiccation. It is a product of diagenesis in an alkaline environment. ## Mineral Associations This mineral often co-occurs with other rare carbonates and evaporites. Typical associated minerals include shortite, trona, nahcolite, northupite, bradleyite, as well as pyrite and dolomite. ## Localities The most important and classic locality for eitelite is the Green River Formation in Wyoming and Utah, USA, where it was discovered. Significant specimens come from the Westvaco mine in Sweetwater County (Wyoming). Outside the USA, its presence has been noted in ultrabasic intrusions on the Kola Peninsula in Russia (Khibiny and Kovdor massifs) and in Uganda (Kalyango volcanic complex).

Rarity

Rare

For collectors

## Quality Criteria The most prized by collectors are large, sharply terminated, transparent, and colorless eitelite crystals that exhibit strong luster. Specimens where a single, well-formed crystal is set on a contrasting rock matrix are particularly sought after. Specimens from the classic Green River Formation locality are the standard for this mineral. ## Popular Localities By far the most known and valued eitelite specimens come from mines within the Green River Formation in Sweetwater County, Wyoming, USA. Most of the material available on the collector's market originates from there. Specimens from Russia or Uganda are much rarer and represent a great curiosity.

Care and storage

## Cleaning Eitelite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its partial solubility in water, contact with water, and especially acids, should be avoided. If liquid is necessary, it is recommended to use pure isopropyl alcohol and dry immediately. ## What to Avoid Contact with water must be absolutely avoided, as it can damage the crystal surfaces or dissolve them. The mineral is sensitive to all acids, which cause it to effervesce violently and be destroyed. It is brittle, so it should be protected from impacts and scratches. It should not be cleaned ultrasonically. ## Storage Collector specimens of eitelite are best stored in closed, dry containers or display cases to protect them from atmospheric moisture and dust. They should be kept away from minerals that could scratch them.

Sources

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