Burkeite

Chemical formula: Na₄(S₆+O₄)(CO₃)

Burkeite is a rare, colorless or white mineral from the sulfate and carbonate group, forming characteristic tabular crystals in evaporite deposits.

## Characteristics Burkeite is a double sulfate and carbonate of sodium, occurring as brittle, tabular or short prismatic crystals. It is usually colorless, white, or grayish, sometimes taking on yellowish or pinkish hues. Crystals often form twins, giving them a characteristic, pseudohexagonal appearance. It occurs as granular aggregates, radial aggregates, or as single, well-formed crystals grown on other minerals. ## Physical Properties This mineral is characterized by a hardness of 3.5 on the Mohs scale and is relatively light, with a density of about 2.57 g/cm³. It has a vitreous luster and is transparent to translucent. It exhibits weak cleavage in one direction and an uneven fracture. It is soluble in water. ## Colors and Varieties Burkeite is most often colorless or white. Impurities can give it a pale yellow, gray, or pink coloration. No named varieties of this mineral are distinguished. ## History and Name The mineral's name honors John A. Burke (1850-1931), an American businessman and one of the founders of the company that exploited deposits in Searles Lake, California. The mineral was first described by William F. Foshag in 1921 based on specimens from this very location. ## Uses Burkeite has no direct industrial applications. It is a mineral primarily of scientific and collector's interest, valued for its well-formed crystals and rarity.

Properties

Mohs hardness: 3.5
Luster: Vitreous
Streak: White
Density: 2.57
Cleavage: Poor on {001}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification A key diagnostic feature of burkeite is its solubility in water. In the field, it can be recognized by its tabular crystal habit, often forming characteristic twins with a hexagonal outline. It occurs in the specific environment of salt lakes (evaporites). ## Distinguishing from Similar Minerals It can be confused with other colorless evaporite minerals such as hanksite, thenardite, or trona. It differs from hanksite in crystal habit (hanksite forms hexagonal prisms) and the absence of the characteristic double pyramid. It is distinguished from thenardite and trona by its crystalline form and chemical tests for the presence of carbonates and sulfates. ## Crystal Forms Burkeite crystals are orthorhombic but often show a pseudohexagonal outline due to twinning. It most often forms flattened, tabular crystals. It also occurs as granular aggregates and radial aggregates.

Geological environment

## Genesis Burkeite is an evaporite mineral. It crystallizes from highly saline, alkaline waters in drying lakes (playas) in arid and hot climates. It forms in deposits rich in sodium sulfate and carbonate. ## Mineral Associations It most often co-occurs with other evaporite minerals such as trona, thenardite, hanksite, halite, northupite, and pirssonite. ## Localities The most important and classic locality for burkeite is Searles Lake in San Bernardino County, California, USA, from which the world's best specimens originate. It also occurs in Deep Spring Lake and Borax Lake in California. Outside the USA, its presence has been reported in alkaline lakes in Turkey (e.g., near Ankara) and Egypt (Wadi El Natrun).

Rarity

Rare

For collectors

## Quality Criteria The most prized by collectors are well-formed, sharp, transparent, and colorless burkeite crystals, especially those exhibiting distinct twinning with a pseudohexagonal outline. The attractiveness of a specimen is enhanced by its size and contrasting placement on a matrix, for example, on hanksite or trona crystals. Specimens from the classic Searles Lake locality are the standard against which others are compared. ## Popular Localities By far the most sought-after and valued specimens come from Searles Lake in California, USA. This is the type locality, which has yielded the largest and best-formed crystals of this mineral.

Care and storage

## Cleaning Burkeite is soluble in water, so it must absolutely not be cleaned wet. To remove dust, use only a soft brush or compressed air from a safe distance. ## What to Avoid Avoid all contact with water, chemical solutions, and high humidity, which can cause it to slowly dissolve and lose its luster. The mineral is brittle and susceptible to mechanical damage. ## Storage Burkeite specimens should be stored in a dry place, preferably in a sealed, lidded display box away from sources of moisture. It is advisable to add a desiccant (e.g., silica gel) to the container.

Sources

IMA Mineral List (CNMNC)