Friedelite Mineral Overview

Mineral name: Friedelite
Mineral class: Silicate (phyllosilicate)

Known Facts

• Chemical formula: Mn₈Si₆O₁₅(OH,Cl)₁₀ (composition varies; chlorine may be present)
• Crystal system: Trigonal
• Mohs hardness: 4–5
• Color range: Pink, reddish-pink, brownish-red, mauve
• Luster: Vitreous to pearly
• Streak: White
• Cleavage: Perfect in one direction (basal)
• Fracture: Uneven
• Specific gravity: Approximately 3.0–3.2
• Common locations: France, South Africa, Sweden, United States
• Uses: Collector specimens, ornamental stone
• Similar minerals: Rhodonite, pyroxmangite, serandite

Physical and Optical Characteristics

Friedelite commonly occurs as:

• Massive or granular aggregates
• Botryoidal or crust-like formations
• Rarely as visible crystals (usually microscopic)

Its most recognizable feature is its pink to reddish coloration, often forming attractive masses in manganese-rich deposits.

The luster ranges from vitreous to pearly, especially on cleavage surfaces. It is typically opaque to translucent.

With a hardness of 4 to 5, Friedelite is moderately soft and can be scratched by harder silicates.

Chemical Composition and Structure

Friedelite is a manganese-rich phyllosilicate, with a variable formula:

• Mn₈Si₆O₁₅(OH,Cl)₁₀

Key features include:

• High manganese (Mn) content, responsible for its color
• Silicate layers, characteristic of phyllosilicates
• Presence of hydroxyl (OH) and sometimes chlorine (Cl)

Its layered structure leads to:

• Perfect basal cleavage
• A somewhat micaceous or platy internal structure

Friedelite belongs to a group of related manganese silicates with similar structures and compositions.

Formation and Geological Occurrence

Friedelite forms in metamorphosed manganese deposits, typically under:

• Low- to medium-grade metamorphic conditions

Common formation environments include:

• Manganese-rich sedimentary rocks that have undergone metamorphism
• Contact metamorphic zones

It is often associated with:

• Rhodonite
• Pyroxmangite
• Hausmannite
• Calcite

These assemblages are typical of manganese-rich metamorphic systems.

Common Locations

Notable occurrences of Friedelite include:

• France: Classic localities (type locality)
• South Africa: Kalahari manganese fields
• Sweden: Manganese deposits
• United States: New Jersey and other manganese-bearing regions

The Kalahari manganese fields are especially well known for high-quality specimens.

Uses and Practical Significance

Friedelite is valued primarily for:

• Mineral collecting: Especially for its distinctive color and association with manganese minerals
• Ornamental use: Occasionally polished for display or lapidary purposes

It has no significant industrial applications.

Similar and Related Minerals

Friedelite may be confused with other pink to red manganese minerals:

• Rhodonite: Typically harder and forms more crystalline masses
• Pyroxmangite: Similar composition but different structure
• Serandite: Often more orange-pink and forms prismatic crystals

Distinguishing Friedelite often relies on:

• Texture (massive vs. crystalline)
• Hardness and cleavage
• Geological context

Identification Notes for Collectors

• Look for pink to reddish massive material in manganese deposits
• Note association with rhodonite and other manganese minerals
• Check for moderate hardness and pearly cleavage surfaces
• Observe lack of well-formed crystals
• Use laboratory analysis for precise identification when needed

Friedelite is a manganese-rich phyllosilicate, recognized for its pink coloration and occurrence in metamorphosed manganese deposits, and is primarily of interest to collectors.