Creedite

Chemical formula: Ca₃Al₂(S₆+O₄)(OH)₂F₈·₂H₂O

Creedite is a rare calcium aluminum fluorosulfate mineral, often found in radial aggregates of crystals with variable color.

## Characteristics Creedite is a calcium aluminum fluorosulfate mineral, typically forming radial aggregates of acicular or prismatic crystals. Specimens often appear as spherical or hemispherical aggregates. Its appearance can be highly varied, from colorless, transparent crystals to specimens with intense colors. ## Physical Properties Creedite has a Mohs hardness of 4, making it a relatively soft mineral. It exhibits a vitreous luster. It is transparent, allowing for observation of its internal structure. The specific gravity of creedite is 2.713, and its streak is white. This mineral has distinct cleavage along the {100} plane. ## Colors and Varieties Creedite occurs in many colors, including white, violet, purple, colorless, and orange. In transmitted light, it is colorless. The variety of colors makes it prized by collectors. ## History and Name Creedite was discovered in 1916. The mineral's name comes from its discovery location – Creed, Colorado, USA. ## Uses Creedite has no industrial applications. It is a mineral valued exclusively by collectors due to its rarity and aesthetics, especially specimens with intense colors and well-formed crystals.

Properties

Mohs hardness: 4
Luster: Vitreous
Streak: white
Density: 2.713
Cleavage: On {100}.
Fracture: Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Creedite can be identified by its characteristic radial aggregates of acicular crystals and vitreous luster. Its Mohs hardness of 4 is also a diagnostic feature. The color, though variable, is often helpful in identification, especially violet or orange hues. ## Differentiation from Similar Minerals Creedite can be confused with other minerals that form radial aggregates, such as scolecite or natrolite. However, it differs from them in chemical composition and physical properties, such as hardness and density. Optical and chemical analysis allows for unambiguous identification. ## Crystal Forms Creedite most often occurs as radial aggregates of acicular or prismatic crystals. Crystals are usually small, forming spherical or hemispherical aggregates. Single, well-formed crystals are less common.

Geological environment

## Genesis Creedite forms in the oxidation zones of fluorite deposits, often in association with other secondary minerals. It forms as a result of low-temperature hydrothermal processes, where solutions rich in fluorine and sulfates react with calcium and aluminum minerals. ## Mineral Associations Creedite often co-occurs with fluorite, barite, calcite, limonite, and other secondary minerals of the oxidation zone. ## Localities The most important creedite localities are in the USA (Creed in Colorado, mines in Arizona), Mexico (La Viesca mine in Coahuila), Russia (Dalnegorsk), and Kazakhstan.

Rarity

Rare

For collectors

## Quality Criteria The most prized creedite specimens are characterized by intense color, especially violet or orange, and well-formed, radial aggregates of crystals. Large, aesthetic aggregates with distinct transparency are particularly sought after. The purity of the specimen and the absence of mechanical damage are also important. ## Popular Localities The most valued creedite specimens come from Creed in Colorado (USA), the La Viesca mine in Mexico, and Dalnegorsk in Russia. Specimens from these localities often stand out for their exceptional aesthetics and color intensity.

Care and storage

## Cleaning Creedite is a relatively soft mineral, so it should be handled with care. For cleaning, it is best to use a soft brush and lukewarm water. For heavier soiling, a mild soap can be used, followed by thorough rinsing of the specimen with distilled water. ## What to Avoid Avoid using aggressive chemical agents, which can damage the mineral's surface. Creedite is sensitive to high temperatures and prolonged exposure to sunlight, which can lead to color fading. Due to the presence of fluorine, avoid contact with acids. The mineral should also be protected from impacts and scratches. ## Storage Creedite is best stored in closed display cases or boxes lined with soft material, away from direct sunlight and heat sources. Maintaining stable temperature and humidity is advisable to prevent potential damage.