Ferroericssonite
Chemical formula: BaFe<sup>2+</sup><sub>2</sub>Fe<sup>3+</sup>(Si<sub>2</sub>O<sub>7</sub>)O(OH)
An extremely rare barium and iron silicate, forming black, tabular crystals in a unique geological environment.
Description
## Characteristics Ferroericssonite is a very rare mineral from the silicate group, being the ferrous (Fe²⁺) analog of ericssonite. It forms thin, tabular or platy crystals of black color and submetallic luster. It usually occurs as small, radial or subparallel aggregates embedded in the host rock. It is an opaque mineral. ## Physical Properties This mineral is characterized by perfect cleavage in one direction, which causes its tendency to separate into thin lamellae. Its luster is described as submetallic to vitreous. The calculated density is 4.71 g/cm³. Hardness has not been precisely determined in available sources. ## Colors and Varieties Ferroericssonite is a mineral of uniform, black color. No color varieties or commercial varieties are known. ## History and Name The mineral's name refers to its chemical composition – it is an analog of ericssonite with dominant iron (Latin: *ferrum*) in place of manganese. It was recognized as a new mineral species by the International Mineralogical Association (IMA) in 1981. ## Applications Due to its extreme rarity and occurrence only in the form of microscopic specimens, ferroericssonite has no industrial application. It is solely an object of scientific and collecting interest.
Diagnostic features
## Identification Characteristic features of ferroericssonite include its black color, tabular crystal habit, perfect cleavage in one direction, and submetallic luster. A key indicator is its unique occurrence environment and paragenesis with other rare barium minerals. ## Distinguishing from Similar Minerals At first glance, it may be confused with other black, platy minerals occurring in the same locality, such as devitoite. Certain differentiation from similar minerals is possible almost exclusively using advanced analytical methods, such as X-ray diffraction (XRD) or X-ray microanalysis (EDS). ## Crystal Forms Ferroericssonite forms very thin, tabular or platy crystals, often with irregular outlines. These crystals arrange themselves into radial, fan-shaped, or almost parallel aggregates, strongly embedded in the rock.
Geological environment
## Genesis Ferroericssonite is a mineral of metamorphic origin. It forms under very specific conditions, in lenses of sanbornite gneisses that have undergone contact metamorphism. These are rocks rich in barium and iron. ## Mineral Associations This mineral coexists with a whole range of other rare barium silicates. Its typical associated minerals include: sanbornite, alforsite, anandite, bario-orthojoaquinite, benitoite, bigcreekite, and devitoite. ## Localities It is a mineral with extremely limited occurrence. The only confirmed location of its discovery in the world is the Esquire No. 7 and No. 8 deposits in the Big Creek area, Fresno County, California, USA.
Rarity
Extremely rare
Collector aspects
## Quality Criteria As a mineral occurring exclusively as micromounts, its collector value depends on several factors. Specimens with well-formed, sharp crystals forming aesthetic aggregates are most highly prized. The abundance of the mineral on the matrix and the presence of rare associated minerals, which enhance the scientific and visual value of the specimen, are also important. ## Popular Localities The only source of ferroericssonite specimens is its type locality in California, USA. All materials available on the collector's market come from this one location.
Care and storage
## Cleaning Ferroericssonite specimens are typically microscopic and very fragile. Cleaning should be kept to an absolute minimum. A photographic blower brush is best for removing dust. Any contact with water or chemicals is discouraged, especially if the mineral is on a sensitive rock matrix. ## What to Avoid Avoid ultrasonic cleaners, which can damage delicate crystals. Protect specimens from shocks, impacts, and sudden temperature changes. Do not expose them to any acids or detergents. ## Storage As a micromount mineral, ferroericssonite should be stored in specialized, sealed boxes that protect it from dust and mechanical damage. Store in stable room conditions, away from sources of vibration.