Antimony Ore Processing from Stibnite

shaking tables and spiral chutes in operation

Antimony is a critical industrial metal widely used in flame retardants, alloys, batteries, and semiconductors. Stibnite (Sb₂S₃) is the primary and most economically important antimony mineral. Efficient antimony ore processing from stibnite is essential to achieve high recovery rates and produce marketable antimony concentrates or metal products. This article provides a comprehensive guide to stibnite beneficiation methods, equipment selection, and processing flowsheets.

Stibnite is a sulfide mineral characterized by:

• High specific gravity

• Brittle texture and easy cleavage

• Strong natural floatability

• Association with quartz, calcite, pyrite, and arsenopyrite

Because stibnite is soft and friable, it is prone to over-grinding, which can negatively affect flotation recovery. Therefore, careful control of crushing and grinding stages is critical.

The most common processing routes for stibnite ores include:

• Gravity separation

• Flotation

• Gravity–flotation combined processes

• Pyrometallurgical or hydrometallurgical treatment (downstream)

Among these, flotation is the dominant beneficiation method for fine-grained stibnite ores.

Stage 1: Crushing of Stibnite Ore

1. Purpose of Crushing

Crushing reduces run-of-mine antimony ore to a suitable size for grinding while minimizing the production of slimes.

2. Recommended Crushing Equipment

Jaw Crusher: Primary crushing for large stibnite ore

Hammer Crusher or Impact Crusher: Preferred due to the brittle nature of stibnite

Cone Crusher: Used cautiously to avoid excessive fines

3. Crushing Considerations

Avoid over-crushing to prevent slime generation

Use staged crushing with screening

Target crushed size: ≤20 mm

Stage 2: Grinding of Antimony Ore

1. Grinding Objectives

Grinding liberates stibnite crystals from gangue minerals while preserving particle integrity.

2. Grinding Equipment

Rod Mill: Ideal for reducing over-grinding

Ball Mill: Used in closed circuit with classifiers

3. Optimal Grinding Fineness

Typically 60–70% passing 200 mesh (74 μm)

Coarser grinding is often sufficient due to good floatability

Tip: Over-grinding creates slimes that reduce flotation selectivity and antimony recovery.

Stage 3: Antimony Flotation from Stibnite

1. Why Flotation Works for Stibnite

Stibnite exhibits excellent natural hydrophobicity, making it highly responsive to flotation with minimal reagent consumption.

2. Flotation Process Flow

Ground slurry enters flotation cells

Collectors enhance stibnite hydrophobicity

Air bubbles attach to stibnite particles

Antimony-rich froth is recovered as concentrate

3. Common Flotation Reagents

Collectors: Xanthates (e.g., ethyl or butyl xanthate)

Frothers: Pine oil, MIBC

Regulators: Lime (pH control)

Depressants: Sodium silicate (gangue suppression)

4. Flotation Circuit Design

Rougher–Cleaner flotation for high-grade concentrate

Gravity–flotation combination for coarse stibnite recovery

For coarse-grained stibnite ores, gravity separation is often effective due to the mineral's high density.

Common Gravity Equipment

• Jig separators

• Shaking tables

• Spiral concentrators

Gravity separation reduces flotation feed volume and improves overall recovery.

Key optimization strategies include:

• Controlled crushing to limit fines

• Coarse grinding where possible

• Low reagent dosage flotation

• Pre-recovery of coarse stibnite by gravity methods

• Regular mineralogical analysis

Modern plants increasingly adopt combined beneficiation flowsheets to maximize efficiency.

After beneficiation, antimony concentrate may be:

• Smelted to produce antimony metal

• Roasted to antimony oxide (Sb₂O₃)

• Treated hydrometallurgically for high-purity products

The downstream method depends on concentrate grade and final product requirements.

Antimony is toxic; proper dust and water management is essential

Tailings must be safely contained

Reagent selection should minimize environmental impact

Worker safety protocols are critical during flotation and smelting

Antimony ore processing from stibnite relies on carefully controlled crushing, grinding, gravity separation, and flotation techniques. Due to stibnite's natural floatability and brittle nature, optimized size reduction and flotation conditions are key to achieving high recovery and concentrate grade. By combining appropriate equipment selection with process optimization, mining operations can significantly improve the economic and environmental performance of antimony beneficiation plants.