Jimkrieghite

Chemical formula: Ca(C₂H₃O₃)₁-₂

Jimkrieghite is an extremely rare organic calcium mineral, forming colorless, acicular crystals in oxidized zones of polymetallic deposits.

## Characteristics Jimkrieghite is a mineral from the group of organic substances, specifically hydrated calcium acetate. It occurs as small, colorless, acicular or hair-like crystals, which form small, radial aggregates or crusts. Individual crystals are usually microscopic in size, rarely exceeding 1 mm in length. Due to its delicate nature and small size, it is a mineral of interest mainly to specialized collectors and scientists. ## Physical Properties Jimkrieghite crystals exhibit a vitreous luster and are transparent. This mineral is very soft, with a Mohs hardness of only 1.5. It is also very light, with a density close to that of water. Its brittleness and low hardness make it exceptionally susceptible to mechanical damage. ## Colors and Varieties Jimkrieghite is colorless. No colored varieties or trade names are known. ## History and Name The mineral was discovered in the Rowley Mine in Maricopa County, Arizona (USA) and officially recognized by the International Mineralogical Association (IMA) in 2022 (IMA2022-093). The name honors Jim Kriegh, an American mineral collector, who was one of the discoverers of this mineral and made significant contributions to the study of the mineralogy of the Rowley Mine. ## Uses Jimkrieghite has no industrial application. Its significance is purely scientific and for collectors.

Properties

Mohs hardness: 1.5
Luster: Vitreous
Streak: White
Density: 1.5
Cleavage: None
Fracture: Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Jimkrieghite is difficult to identify visually without specialized equipment. Characteristic features are very small, colorless, acicular crystals forming radial aggregates on host rocks from the Rowley Mine. A key diagnostic feature is its reaction to water – it dissolves in it. Confirmation of identity requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction. ## Distinguishing from Similar Minerals It can be confused with other secondary sulfate or carbonate minerals of similar appearance, such as gypsum (especially its acicular variety), aragonite, or calcite. Jimkrieghite differs from them by its extremely low hardness (1.5 on the Mohs scale compared to 2 for gypsum and 3 for calcite) and its solubility in water. ## Crystal Forms This mineral forms elongated, acicular or hair-like crystals, often grouped into radial or chaotic aggregates. It also occurs as delicate crusts on other minerals.

Geological environment

## Genesis Jimkrieghite is a secondary mineral, forming in the oxidation zones of polymetallic deposits. Its genesis is related to chemical reactions occurring in post-mining conditions, probably as a result of the interaction of calcium-rich solutions with organic materials (e.g., mine timber) or the activity of microorganisms in the mine environment. ## Mineral Associations At the type locality (Rowley Mine), it co-occurs with minerals such as wulfenite, mimetite, fluorite, barite, quartz, and iron and manganese oxides. ## Localities The only confirmed occurrence of jimkrieghite in the world is the Rowley Mine, located in the Painted Rock Mountains mining district in Maricopa County, Arizona, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a jimkrieghite specimen primarily depends on the richness and aesthetics of the crystal aggregates. Most valued are specimens with clearly visible, well-formed, radial groups of acicular crystals, contrasting with a colorful rock matrix (e.g., orange wulfenite or green mimetite). Due to the microscopic size of the crystals, specimens are mainly evaluated under magnification. ## Popular Localities The only source of specimens is the Rowley Mine in Arizona, USA. This is the type locality, and all specimens available on the collector's market originate from there.

Care and storage

## Cleaning Specimens of jimkrieghite should not be cleaned wet. The mineral is soluble in water and acids. To remove dust, a very soft brush or a photographic air blower can be used very carefully. ## What to Avoid Contact with water, all liquids, and chemicals must be absolutely avoided. The mineral is very soft and brittle, so it must be protected from shocks, impacts, and abrasion. High humidity should also be avoided. ## Storage Specimens should be stored in a dry place, preferably in a sealed, lockable collector's box (a "micromount box"), which protects against dust, moisture, and mechanical damage. It should not be exposed to direct sunlight.

Sources

IMA Mineral List (CNMNC)