Shortite

Chemical formula: Na₂Ca₂(CO₃)₃

Shortite is a rare carbonate mineral, forming characteristic, sharp-edged crystals in the lake sediments of the Green River Formation in the USA.

## Characteristics Shortite is an anhydrous sodium and calcium carbonate, known for forming well-developed, single crystals. Typical specimens are tabular or short prismatic crystals with a characteristic wedge-shaped termination, which is a result of their hemimorphic structure. The mineral is usually colorless, white, or takes on pale yellow and greenish hues. It exhibits a vitreous luster on crystal faces and fracture. It is prized by collectors specializing in rare minerals and specimens from the Green River Formation. ## Physical Properties Shortite is a relatively soft mineral with a Mohs hardness of 3.5-4. Its density is approximately 2.63 g/cm³. It is transparent to translucent. It exhibits distinct fluorescence – it glows blue under shortwave UV light and creamy white under longwave UV light. It is soluble in water and acids. ## Colors and Varieties This mineral does not form colored varieties or have commercial names. Its coloration is usually uniform, ranging from colorless, through white, to pale yellow. ## History and Name Shortite was first described in 1939 by Joseph J. Fahey. The mineral is named in honor of Maxwell N. Short (1889-1952), a professor of optical mineralogy at the University of Arizona, in recognition of his contributions to this field of science. ## Uses Shortite has no industrial applications. It is solely an object of interest for collectors and scientists studying unique evaporitic environments.

Properties

Mohs hardness: 3.5-4
Luster: Vitreous
Streak: White
Density: 2.63
Cleavage: Good on {010}, {011}, and {110}
Fracture: Conchoidal
Transparency: Transparent to Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification The most important diagnostic feature of shortite is its characteristic crystal habit – orthorhombic crystals with wedge-shaped, hemimorphic terminations. Strong blue fluorescence under UV light (shortwave) is also very helpful in identification. Reaction with acids (effervescence) confirms it is a carbonate, and solubility in water distinguishes it from many other carbonates. ## Distinguishing from Similar Minerals Shortite is sometimes confused with other colorless minerals from the Green River Formation, such as pirssonite, gaylussite, or nahcolite. Pirssonite and gaylussite crystallize in the monoclinic system and have different crystal forms. Nahcolite is much softer (2.5 on the Mohs scale). Key for differentiation are crystal form, hardness, and the fluorescence test. ## Crystal Forms Shortite crystals are usually well-formed, single, often doubly terminated. They occur as tabular, prismatic crystals, or in granular aggregates. They are often embedded in a clayey or marly rock mass (marlstone).

Geological environment

## Genesis Shortite is a primary mineral, crystallizing directly from solutions in highly saline and alkaline lakes. Its formation is closely related to an evaporitic environment. It is most commonly found in oil shales and marlstones. ## Mineral Associations This mineral co-occurs with other evaporites typical of its formation environment. The most common associations include: trona, nahcolite, pirssonite, gaylussite, northupite, bradleyite, as well as calcite and dolomite. ## Localities The most important and classic locality for shortite is the Green River Formation in the United States, covering areas of Wyoming, Utah, and Colorado. The most magnificent specimens come from trona mines in Sweetwater County, Wyoming, where this mineral is locally common.

Rarity

Rare

For collectors

## Quality Criteria The most highly prized shortite specimens are large, sharp-edged, and fully transparent crystals. Ideal specimens are free from damage, have a vitreous luster, and are often doubly terminated. Attractive placement of the crystal on the matrix or co-occurrence with other rare minerals from the locality, e.g., northupite, adds significant value. ## Popular Localities By far the best and most sought-after shortite specimens come from mines in the Green River Basin, especially from the Westvaco mine in Sweetwater County, Wyoming, USA. Specimens from this locality represent the global standard for this mineral.

Care and storage

## Cleaning Shortite is soluble in water, so it must not be cleaned wet under any circumstances. Any contaminants should be removed only dry, using a soft brush, a photographic air blower, or compressed air from a safe distance. ## What to Avoid Contact with water, water vapor, and other liquids must be absolutely avoided. The mineral is sensitive to acids, with which it reacts violently. Due to its relatively low hardness and good cleavage, it is susceptible to scratches and mechanical damage. It should be protected from impacts and falls. ## Storage Shortite specimens are best stored in a dry place, in closed containers or display cases that protect against moisture and dust. Boxes with a desiccant are a good solution. Avoid sudden temperature changes.