Satterlyite

Chemical formula: (Fe<sup>2+</sup>,Mg,Fe<sup>3+</sup>)<sub>12</sub>(PO<sub>3</sub>OH)(PO<sub>4</sub>)<sub>5</sub>(OH,O)<sub>6</sub>

Satterlyite is a rare phosphate mineral, forming hexagonal crystals and brown aggregates, known primarily from unique parageneses in Canada.

## Characteristics Satterlyite is a complex iron and magnesium phosphate. It most commonly occurs as radial or lamellar aggregates, as well as well-formed, hexagonal, tabular crystals. Specimens typically range in color from yellowish-brown, through reddish-brown, to dark brown. The mineral is sometimes found within phosphate nodules (concretions) in sedimentary rocks. ## Physical Properties The Mohs hardness of satterlyite is 4.5-5, classifying it as a mineral of medium hardness. It has a density in the range of 3.65-3.75 g/cm³. It is characterized by a vitreous to resinous luster and is translucent to opaque. It exhibits perfect cleavage in one plane, perpendicular to the main crystal axis. ## Colors and Varieties This mineral does not form color varieties or commercial forms. Its coloration is uniform and limited to shades of brown – from yellowish to reddish and dark brown. The color is associated with the presence of iron ions in various oxidation states. ## History and Name Satterlyite was first described in 1978 by Joseph A. Mandarino, B. D. Sturman, and J. Corlett. Its name honors Jack Satterly (1906–1993), a Canadian geologist who worked for the Ontario Department of Mines, for his contributions to Canadian geology. The type locality, from which the first described specimens originated, is the Big Fish River area in Yukon Territory, Canada. ## Uses Due to its rarity, satterlyite has no industrial applications. It is solely an object of scientific interest and a prized acquisition for advanced systematic and regional mineral collections.

Properties

Mohs hardness
4.5-5
Luster
Vitreous to Resinous
Streak
Pale brown
Density
3.65-3.75
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Translucent to Opaque
Crystal system
Hexagonal

Diagnostic features

## Identification A key diagnostic feature of satterlyite is its perfect cleavage in one direction (basal), which causes the mineral to easily split into thin plates. The hexagonal crystal shape (if visible), brown color, and vitreous or resinous luster are also helpful. Occurrence in nodules within siderite mudstones is also a strong indicator. ## Distinguishing from Similar Minerals Satterlyite can be confused with other brown tabular minerals, such as micas (e.g., biotite) or siderite. It differs from mica by its greater hardness and lack of elasticity of the lamellae. Siderite crystallizes in the trigonal system and has perfect rhombohedral cleavage (in three directions), not in one plane. The characteristic paragenesis with other rare phosphates from Yukon is often decisive for correct identification. ## Crystal Forms Satterlyite crystals have a tabular or short prismatic habit with a hexagonal outline. However, it most often forms lamellar, rosette-like, or radial aggregates, and also occurs as granular masses within phosphate nodules.

Geological environment

## Genesis Satterlyite is a mineral of sedimentary or early metamorphic origin. It forms under specific conditions, within phosphatic-ferruginous concretions (nodules) embedded in organic-rich siderite mudstones. Its crystallization is associated with diagenetic processes in a reducing environment. ## Mineral Associations This mineral co-occurs with other, often rare, phosphates. Its typical associated minerals include maricite, wicksite, wolfeite, goethite, pyrite, quartz, and minerals from the vivianite group. This paragenesis is characteristic of its type locality. ## Localities The most important and practically only commercially significant occurrence of satterlyite in the world is the area along the Big Fish and Rapid Creek rivers in Yukon Territory, Canada. This is a world-renowned locality known for the occurrence of unique phosphate minerals.

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued satterlyite specimens are those that contain well-formed, sharp, hexagonal crystals with a distinct luster. The richness of the specimen and its association with other rare and visually attractive minerals from this locality, such as lazulite, wardite, or wicksite, are also of great importance. The clarity of the crystals and their aesthetic arrangement on the rock matrix significantly increase their collector's value. ## Popular Localities The vast majority of specimens available on the collector's market come from a single region: Big Fish River - Rapid Creek in Yukon Territory, Canada. Specimens from this locality are the standard for this mineral.

Care and storage

## Cleaning Satterlyite specimens should be cleaned very carefully, preferably dry, using a soft brush. If necessary, distilled water can be used. Due to its perfect cleavage, ultrasonic cleaners should be avoided, as they could cause the specimen to break apart along cleavage planes. ## What to Avoid The mineral is sensitive to acids. It should be protected from contact with chemicals. Due to its medium hardness and perfect cleavage, it is susceptible to mechanical damage – scratches and impacts. It is not advisable to expose it to prolonged direct sunlight, although its sensitivity to this factor is not documented. ## Storage Satterlyite should be stored in a separate, padded collector's box to avoid contact with harder minerals. Protect from dust, moisture, and sudden temperature changes. Its brittleness makes it unsuitable for jewelry mounting.

External references

Sources

Read more