Gordonite

Chemical formula: MgAl<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·8H<sub>2</sub>O

Gordonite is a rare, hydrated magnesium aluminum phosphate, forming colorless or white crystals with a vitreous luster.

## Characteristics Gordonite is a rare, hydrated phosphate mineral belonging to the laueite group. It typically forms small, tabular or bladed crystals, which can be aggregated into radial clusters or rosettes. Specimens are most often colorless, white, or pale yellow and are characterized by a vitreous luster, and a pearly luster on cleavage surfaces. Due to its rarity and delicate structure, it is a mineral valued mainly by collectors. ## Physical Properties Gordonite crystals are relatively soft, with a hardness of approximately 3 on the Mohs scale. They are brittle, and their density is about 2.2 g/cm³. The mineral is transparent to translucent. It exhibits perfect cleavage in one direction, which is visible as a pearly luster on fracture planes. ## Colors and Varieties Gordonite occurs in a limited color range. Colorless and white specimens are most common. Less frequently, it takes on shades of pale yellow, pinkish, or light brown, which is usually associated with the presence of impurities. No named varieties are distinguished. ## History and Name 1930 by John W. Gruner and D.Z. McConnell. The name "gordonite" was given in honor of Samuel George Gordon (1897-1952), an American mineralogist and crystallographer from the Academy of Natural Sciences of Philadelphia, in recognition of his contributions to mineralogy. ## Uses Gordonite has no industrial application. Its significance is purely scientific and collectible.

Properties

Mohs hardness
3
Luster
Vitreous, Pearly
Streak
White
Density
2.21
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Triclinic

Diagnostic features

## Identification Gordonite can be recognized by its characteristic, thin, tabular crystals, often forming radial aggregates. Key features include a vitreous or pearly luster, low hardness (about 3 on the Mohs scale), and perfect cleavage in one direction. It occurs in a typical environment of secondary phosphate minerals. ## Distinguishing from Similar Minerals Gordonite is sometimes confused with other colorless or white phosphate minerals, such as wardite, strengite, or variscite. It is distinguished from them by its specific crystal habit (thin tablets), perfect cleavage, and co-occurrence with other minerals from its paragenesis. Accurate identification often requires chemical analysis (EDS) or X-ray diffraction (XRD). ## Crystal Forms Gordonite crystals are triclinic and develop as thin to thick tablets, often with a hexagonal or octagonal outline. They commonly form fan-shaped or radial aggregates and rosettes, as well as spherical clusters. Less frequently, they occur as single, well-formed crystals.

Geological environment

## Genesis Gordonite is a secondary phosphate mineral. It forms as a result of hydrothermal processes or weathering in the oxidation zones of phosphate deposits, particularly in caves rich in bat guano, where reactions occur between phosphate solutions and clay minerals or aluminosilicates of the surrounding rocks. ## Mineral Associations This mineral often co-occurs with other secondary phosphates. Its most common associations include: montgomeryite, overite, strengite, wardite, variscite, fluellite, crandallite, millisite, and minerals from the apatite group. ## Localities The most important and classic locality for gordonite is Clay Canyon cave near Fairfield, Utah, USA, from which the best known specimens originate. It is also known from the Tip Top mine in Custer County, South Dakota (USA), and from several other less significant localities worldwide, including Germany and Namibia.

Rarity

Rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp, and transparent crystals, forming aesthetic, radial aggregates or rosettes. Purity and lack of damage to the delicate crystals are highly prized. Specimens on a contrasting rock matrix are more desirable than loose aggregates. Size matters – larger, well-formed rosettes command higher prices. ## Popular Localities By far the most sought-after and classic gordonite specimens come from Clay Canyon cave in Utah, USA. This locality has provided specimens considered the world standard for this mineral. Specimens from the Tip Top mine in South Dakota are also valued in collections.

Care and storage

## Cleaning Gordonite specimens should be cleaned with the utmost care, using a soft brush to remove dust. Due to its softness and perfect cleavage, ultrasonic cleaners and mechanical cleaning should be avoided. If liquid is necessary, brief contact with distilled water is recommended, followed by thorough drying of the specimen at room temperature. ## What to Avoid Contact with acids and other chemicals that can damage the mineral should be avoided. Gordonite is sensitive to high temperatures, which can lead to its dehydration and destruction of its structure. It should be protected from prolonged exposure to direct sunlight and moisture. ## Storage It is recommended to store gordonite specimens in separate, padded collector boxes to protect them from mechanical damage and scratching by harder minerals. Stable environmental conditions should be ensured, away from sources of heat and moisture.

Sources

Read more