Teepleite

Chemical formula: Na₂B(OH)₄Cl

Teepleite is a rare sodium borate, forming colorless or white, short-prismatic crystals with a vitreous luster.

## Characteristics Teepleite is a hydrated sodium borate and chloride. It occurs as short, prismatic or dipyramidal crystals, rarely exceeding a few millimeters in length. They are typically colorless or white, occasionally taking on a pale beige hue. This mineral is transparent to translucent and exhibits a vitreous luster on crystal faces. ## Physical Properties Teepleite is a relatively soft mineral with a hardness of 3-3.5 on the Mohs scale. Its density is approximately 2.076 g/cm³, making it quite light. It is brittle, and its fracture is uneven or conchoidal. This mineral is soluble in water. ## Colors and Varieties This mineral does not form colored varieties. Its coloration is uniform and limited to shades of white, beige, and colorless. In transmitted light, it is always colorless. ## History and Name Teepleite was first described in 1938. Its name honors John Edgar Teeple (1874-1931), an American chemical engineer and treasurer of the American Chemical Society, in recognition of his contributions to the study of borate chemistry and industry at Searles Lake, California. ## Uses Due to its rarity and small crystal size, teepleite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or borate minerals.

Properties

Mohs hardness
3-3.5
Luster
Vitreous
Streak
White
Density
2.076
Cleavage
None
Fracture
Irregular/Uneven,Sub-Conchoidal
Transparency
Transparent,Translucent
Crystal system
Tetragonal

Diagnostic features

## Identification Teepleite is recognized by its characteristic short, tetragonal crystals, vitreous luster, and low hardness. A key diagnostic feature is its solubility in water. It reacts with acids. ## Distinguishing from Similar Minerals It can be confused with other colorless borates or halides found in similar environments, such as borax or halite. It differs from borax by its crystal habit (tetragonal, not monoclinic) and lack of characteristic surface efflorescence. It differs from halite by its crystal habit (prismatic/dipyramidal instead of cubic) and lower hardness. ## Crystal Forms It forms well-developed, short-prismatic crystals with a square cross-section, terminated by faces of a tetragonal dipyramid. Less commonly, it occurs as granular aggregates.

Geological environment

## Genesis Teepleite is an evaporite mineral. It forms by precipitation from highly saline, boron- and chlorine-rich waters of saline lakes (playas) under arid and hot climatic conditions. It crystallizes directly from solution or in bottom sediments. ## Mineral Associations This mineral co-occurs with other evaporites, such as borax, tincalconite, halite, thermonatrite, as well as northupite and pirssonite. ## Localities The most important and type locality for teepleite is Borax Lake in Lake County, California, USA. It is also found in other dry lakes in California (Searles Lake, Deep Spring Lake) and in Bolivia (Laguna Salinas, Potosí department).

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with sharp, well-formed, transparent crystals with a vitreous luster. Single, freestanding crystals, as well as groups of crystals grown on a contrasting matrix, are highly valued. Size is a key factor – crystals exceeding a few millimeters are considered significant. ## Popular Localities By far, the most desirable specimens come from the type locality – Borax Lake in California. Material from this location is considered classic and serves as the standard for this mineral.

Care and storage

## Cleaning Teepleite specimens should be cleaned with the utmost care, dry-cleaned only, using a soft brush to remove dust. Contact with water, even distilled, will cause it to dissolve. ## What to Avoid Contact with water and all liquids, including cleaning agents, must be strictly avoided. The mineral is sensitive to humid air, which can cause its slow degradation. It should be protected from high temperatures and direct sunlight. ## Storage It is recommended to store teepleite in tightly sealed, dry containers (e.g., "perky boxes") with a desiccant (silica gel). Display should be in enclosed showcases, away from sources of moisture and heat.

External references

Sources

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