Neotocite

Chemical formula: (Mn²⁺,Fe²⁺)SiO₃·H₂O

Neotocite is a hydrated manganese and iron silicate, forming amorphous, vitreous masses ranging in color from yellowish-brown to black, often found in the oxidation zones of manganese deposits.

## Characteristics Neotocite is an amorphous (non-crystalline), hydrated manganese and iron silicate, classified as a mineraloid. It typically occurs in compact, reniform, botryoidal masses, or as earthy masses and crusts. Its appearance is often similar to enamel or resin, and due to the lack of crystalline structure, it does not form well-developed crystals. Over time, it can undergo dehydration and recrystallization into other, more stable manganese minerals. ## Physical Properties Neotocite is characterized by a Mohs hardness of 3-4. Its luster is typically vitreous to resinous, becoming dull on weathered surfaces. It is brittle, and its fracture is conchoidal to uneven. The density ranges from 2.7 to 2.9 g/cm³. As an amorphous substance, it does not exhibit cleavage. ## Colors and Varieties The color of neotocite is variable, most often taking on shades from yellowish-brown, through reddish-brown, dark brown, to black. Thinner fragments may be translucent in shades of brown or yellow. No named varieties of this mineraloid are distinguished. ## History and Name The name neotocite comes from the Greek words *neos* (new) and *tokos* (birth, origin), referring to the fact that it forms as a result of the alteration of other manganese minerals, such as rhodonite. It was first described in 1849 based on specimens from Sweden. ## Uses Neotocite has no significant industrial use. It constitutes a minor manganese ore if it occurs in large accumulations. For collectors, it is interesting as a weathering product and a component of parageneses in manganese deposits.

Properties

Mohs hardness: 3-4
Color: Black, dark brown to dark olive-green, dark red-brown
Luster: Vitreous to resinous
Streak: Dark brown to black
Density: 2.43
Cleavage: None
Fracture: Conchoidal,Sub-Conchoidal
Transparency: Transparent,Translucent
Crystal system: Amorphous

Diagnostic features

## Identification Neotocite is identified by its amorphous, vitreous or resinous form, conchoidal fracture, and relatively low hardness. Its occurrence as compact, reniform, or botryoidal masses in the oxidation zones of manganese deposits is characteristic. Its brown to black color and brownish streak are also important clues. ## Distinguishing from Similar Minerals Neotocite is sometimes confused with other amorphous manganese oxides and silicates, such as wad or psilomelane. It differs from them by its lower hardness and often lighter, brownish streak (psilomelane has a black streak). It can also be mistaken for opal or obsidian, but the geological context (associations with manganese minerals) is crucial for correct identification. ## Crystal Forms As an amorphous mineraloid, neotocite does not form crystals. It occurs exclusively in aggregate forms: compact, massive, reniform, botryoidal, as well as crusts and fillings.

Geological environment

## Genesis Neotocite is a secondary mineral, forming in the oxidation (weathering) zones of manganese deposits. It forms as a result of hydrothermal alteration or weathering of primary manganese minerals, such as rhodonite, pyroxmangite, or manganese carbonates (rhodochrosite). It is a low-temperature product. ## Mineral Associations It most often co-occurs with minerals from which it forms or which it accompanies in the oxidation zone. Typical associated minerals include rhodonite, rhodochrosite, pyroxmangite, bustamite, quartz, calcite, and also manganese oxides like pyrolusite, psilomelane, and wad. ## Localities Significant neotocite localities are found in Sweden (Långban and Nordmark mines), from where the first described specimens originated. Other important localities include Broken Hill in Australia; Franklin and Sterling Hill in New Jersey, USA; as well as deposits in Japan, the Republic of South Africa, and Kazakhstan.

Rarity

Not very common

For collectors

## Quality Criteria The collector appeal of neotocite depends on the form of its aggregates and its association with other minerals. Specimens with well-formed reniform or botryoidal shapes and an intense, vitreous luster are most valued. Specimens that are pseudomorphs after other minerals (e.g., after rhodonite) or that form aesthetic compositions with contrasting minerals, such as pink rhodonite or white calcite, also have high value. ## Popular Localities Classic and most prized specimens come from historical localities in Sweden (Långban) and Franklin, USA. Specimens from Broken Hill, Australia, are also sought after by collectors due to their rich mineral parageneses.

Care and storage

## Cleaning Neotocite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, a damp (not wet) cloth or a cotton swab moistened with distilled water can be used, avoiding excessive soaking. Ultrasonic cleaners should be avoided. ## What to Avoid Neotocite is sensitive to chemicals, especially acids, which can damage it. It should be protected from high temperatures, which can cause water loss and structural changes. Prolonged exposure to direct sunlight is not recommended. ## Storage Specimens should be stored in stable conditions, away from sources of heat and humidity. It is best to keep them in separate, padded boxes or on stable stands in a display cabinet to prevent scratches and chips, to which it is susceptible due to its brittleness and low hardness.

External references

https://www.mindat.org/min-2879.html