Paceite

Chemical formula: CaCu<sup>2+</sup>(CH<sub>3</sub>COO)<sup>1-</sup><sub>4</sub>·6H<sub>2</sub>O

Paceite is a very rare, synthetic mineral from the acetate group, valued for its intensely blue, well-formed crystals.

## Characteristics Paceite is a hydrated calcium copper acetate, belonging to the group of organic minerals. It forms characteristic, prismatic or tabular crystals of an intense blue color, resembling chalcanthite. It is a synthetic mineral, formed accidentally as a result of chemical reactions in a specific, man-made environment. Its crystals are usually small but well-formed and transparent, making them attractive objects for collectors specializing in rare or anthropogenic minerals. ## Physical Properties Paceite crystals exhibit a hardness of about 2 on the Mohs scale, meaning they are very soft and prone to scratching. They have a vitreous luster and are transparent to translucent. The mineral's density is approximately 1.65 g/cm³, making it relatively light. It is brittle and easily susceptible to mechanical damage. ## Colors and Varieties This mineral occurs in a uniform, intense, azure or sky-blue color. No color or commercial varieties are known. ## History and Name The name paceite honors Frank Pace (born 1946), an American mineral collector from Houston, Texas, who first found and drew attention to this unusual material. The substance was described as a new mineral in 2002 by Joel D. Grice, Robert A. Gault, and John A. Bending. Type specimens come from Frank Pace's collection and are housed at the Canadian Museum of Nature in Ottawa. ## Uses Paceite has no industrial applications. Its significance is purely scientific and collectible, as an example of a rare organic mineral formed under anthropogenic conditions.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
Light blue
Density
1.65
Cleavage
Good on {110}
Fracture
Conchoidal
Transparency
Transparent to translucent
Crystal system
Tetragonal

Diagnostic features

## Identification Paceite is relatively easy to identify based on its intensely blue color, characteristic crystal shape, and origin from a specific, unusual locality. Its extreme softness (hardness 2) and water solubility are key diagnostic features. ## Distinguishing from Similar Minerals This mineral is sometimes confused with chalcanthite (CuSO₄·5H₂O) due to its similar, intensely blue color. However, paceite differs in its tetragonal crystal system (chalcanthite crystallizes in the triclinic system) and genesis – it is an acetate, not a sulfate. Unlike chalcanthite, paceite does not have an astringent, metallic taste and is associated with a specific, anthropogenic environment. ## Crystal Forms Paceite crystallizes in the tetragonal system, forming simple, elongated prismatic crystals or thick tabular crystals. Characteristic striations are often present on them. Crystals are usually well-formed and grow on the substrate in the form of small aggregates.

Geological environment

## Genesis Paceite is a secondary mineral of anthropogenic origin. It formed as a result of an accidental chemical reaction in an unusual environment. Crystals crystallized on the surface of wooden beams in an abandoned building in Texas. Its genesis is believed to be related to the reaction of acetate solutions (likely originating from the decomposition of organic materials or pollutants) with copper and calcium ions, which may have been present in rainwater or derived from nearby building materials. ## Mineral Associations On original specimens, paceite does not co-occur with other crystalline minerals. It grows directly on weathered wood. ## Localities The only confirmed occurrence (type locality) of paceite is an abandoned building in Harris County, Texas, USA. It is a mineral known exclusively from this one very specific locality.

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued paceite specimens are those with large, sharply terminated, transparent crystals of an intensely blue color. The aesthetics of the composition are important – an attractive arrangement of crystals on a small fragment of the original wooden substrate. Specimens without mechanical damage, with distinct faces and edges, achieve the highest value. ## Popular Localities Since this mineral originates from only one place in the world (an abandoned building in Texas), all specimens available on the collector's market come from there. This locality is considered classic and unique for this species.

Care and storage

## Cleaning Paceite specimens should be cleaned with the utmost care, using only compressed air to remove dust. Any contact with water, even distilled, or other liquids is highly inadvisable, as the mineral is soluble in them. ## What to Avoid Contact with water and all chemicals must be strictly avoided. The mineral is sensitive to elevated temperatures, which can lead to its dehydration and destruction. It should be protected from direct sunlight, which can cause fading, and from changes in humidity, which can lead to crystal disintegration. ## Storage It is recommended to store paceite in tightly sealed, dry containers (e.g., "perky box" type) away from heat and light sources. It is best kept under stable room conditions, away from moisture. Due to its brittleness and softness, vibrations and contact with harder minerals should be avoided.

Sources

Read more