Paulingite-K

Chemical formula: (K,Ca,Na,Ba,&#₉₇₂₃;)₁₀(Si,Al)₄₂O₈₄·₃₄H₂O

Paulingite-K is a rare potassium zeolite, forming characteristic spherical aggregates of isometric crystals with a vitreous luster.

## Characteristics Paulingite-K is a hydrated potassium, calcium, and sodium aluminosilicate, belonging to the zeolite group. This mineral forms very characteristic, almost perfectly spherical aggregates, composed of small, highly lustrous crystals. Individual crystals are usually too small to be seen with the naked eye, but together they form spherical shapes up to several millimeters in diameter. The surface of the aggregates is often faceted, giving them the appearance of small, cut spheres or disks. ## Physical Properties Paulingite-K crystals have a hardness of about 5 on the Mohs scale. They exhibit a vitreous, sometimes slightly pearly luster. They are transparent to translucent. The mineral's density is approximately 2.1-2.2 g/cm³. ## Colors and Varieties Paulingite-K is most commonly colorless or white. Rarer specimens may have a delicate, yellowish tint. No distinct color varieties or commercial names are recognized. ## History and Name The mineral was named in 1960 in honor of Linus Pauling (1901-1994), an American chemist and crystallographer, two-time Nobel Prize laureate, for his fundamental contributions to understanding complex silicate structures. It was originally described as "paulingite," and the "-K" suffix was added later when chemical analysis revealed the dominance of potassium (K) in its composition relative to other paulingites (e.g., Paulingite-Ca). ## Uses Paulingite-K has no industrial applications. However, it is a highly valued and sought-after mineral by collectors specializing in zeolites and rare minerals.

Properties

Mohs hardness: 5
Color: Colorless to pale yellow
Luster: Vitreous , Greasy
Streak: White
Density: 0
Cleavage: Imperfect on {100}
Fracture: Uneven
Transparency: Transparent
Crystal system: Isometric

Diagnostic features

## Identification The most characteristic feature of paulingite-K is its perfectly spherical or spheroidal crystal aggregates. The luster and crystal form are key for identification. It occurs in gas vesicles in basaltic rocks. ## Distinguishing from Similar Minerals Spherical paulingite-K aggregates can be confused with other zeolites that form spherulites, such as thomsonite or some forms of chabazite. However, paulingite-K is distinguished by the more regular, isometric shape of the individual crystals forming the aggregate (often visible under magnification as small rhombohedra) and the characteristic, almost "faceted" appearance of the sphere's surface. ## Crystal Forms Paulingite-K crystallizes in the isometric system, most often forming crystals with a rhombic dodecahedron habit. These crystals rarely occur individually, almost always coalescing into spherical or hemispherical aggregates.

Geological environment

## Genesis Paulingite-K is a low-temperature hydrothermal mineral. It forms in vesicles and fractures in volcanic rocks, primarily basalts. It crystallizes from silica- and alkali-rich solutions during the late stages of lava cooling. ## Mineral Associations It most commonly co-occurs with other zeolites, such as phillipsite, chabazite, gismondine, as well as with calcite and apophyllite. ## Localities The most important and well-known localities for paulingite-K are found in basalts along the Columbia River in Washington and Oregon states, USA. It is also known from Riggins in Idaho (USA), Höwenegg in Germany, and from some localities in Iceland and the Czech Republic (near Ústí nad Labem).

Rarity

Rare

For collectors

## Quality Criteria The most highly prized paulingite-K specimens are those with well-formed, perfectly spherical aggregates of high luster and significant diameter. The contrasting placement of colorless or white spheres on a dark basalt matrix significantly enhances the visual appeal and value of the specimen. Size is also important – aggregates exceeding 5 mm in diameter are considered large and rare. ## Popular Localities The localities along the Columbia River, especially around Rock Island Dam in Washington State, USA, are considered classic and yield the best specimens. Specimens from these locations serve as a benchmark for this mineral.

Care and storage

## Cleaning Specimens should only be cleaned with lukewarm distilled water, using a very soft brush to remove dust. Ultrasonic cleaners should be avoided, as they can damage delicate aggregates. ## What to Avoid As a zeolite, paulingite-K is sensitive to high temperatures, which can cause the loss of water from its structure and destroy the crystals. Contact with acids and other chemicals should be avoided. Prolonged exposure to strong sunlight is not recommended. ## Storage Specimens are best stored in closed, stable containers or display cases to protect them from dust and mechanical damage. Due to its fragility, other minerals should be avoided from being placed directly on paulingite-K specimens.