Graphite Ore and Its Mineral Processing: Analysis and Application

The commercial value of graphite ore depends on grade, flake size, and impurity content. Flake graphite (especially large flakes) holds higher market value, while amorphous graphite is mainly used in low-end applications due to processing challenges. With the rise of the new energy sector, demand for high-purity graphite continues to grow, driving advancements in beneficiation and purification techniques. Let’s follow us to learn about graphite ore and its beneficiation methods.

 

Comprehensive Introduction to Graphite Ore

1. Overview

Graphite ore is a mineral resource primarily composed of natural graphite (crystalline carbon). It exhibits properties such as high-temperature resistance, electrical and thermal conductivity, lubricity, and chemical stability. Based on crystallinity, it can be classified into crystalline graphite (flake graphite) and amorphous graphite (microcrystalline or “earthy” graphite). These types find extensive applications in metallurgy, batteries, lubricants, refractory materials, and the nuclear industry.

 

2. Grade (Quality)

The quality of graphite ore is typically measured by its fixed carbon (FC) content, determined through chemical analysis (e.g., high-temperature combustion method).

Industrial Requirements For Graphite Mines
Crystalline graphite	Cutoff grade: 2.5%	Poor ore: 3-5%	Rich ore: ≥5%
amorphous graphite	Cutoff grade: 60%	Poor ore: 65-80%	Rich ore: ≥80%

 

The industrially recoverable grade of crystalline graphite (flake graphite) is usually ≥2.5%, and high-quality ore can reach 10%~20%. Cryptocrystalline graphite with a grade of less than 65% is generally not mined, and its natural grade is higher at 60%~85%, but due to its fine embedding, it is difficult to purify. Cryptocrystalline graphite with a grade greater than 80% is ground and sold directly. For high-purity graphite requirements (such as battery-negative electrode materials), it needs to be purified to more than 99.9%.

 

Crystalline graphite (flake-like) can be used after beneficiation.

Concentrate Grade Requirements
Ordinary flakes	Pencil graphite	Electrical carbon graphite
≥89%	89%-98%	70%-99% or more

 

 

3. Major Mineral Composition & Associated Minerals

The main mineral components of graphite ore include not only graphite itself but also other minerals that coexist with it. These associated minerals will affect the ore dressing process and final application. The following are the main mineral classifications and characteristics commonly found in graphite ores:

 

Graphite

Chemical formula: C (carbon)

Types
Crystalline graphite (flake graphite): It has a hexagonal flake structure, excellent conductivity, and heat resistance, and is used in high-value-added products (such as battery negative electrodes).
Aphanitic graphite (earthy graphite): The microscopic crystals are extremely small (<1μm), the texture is soft, the purity is high, but the ore dressing is difficult, and it is mostly used directly for casting coatings, etc.

Characteristics

Density: 2.09-2.23 g/cm³

Mohs hardness: 1-2 (extremely soft)

Refractory: Melting point > 3000℃

 

 

Main associated minerals

Graphite ore often coexists with the following minerals and needs to be separated by ore dressing:

(1) Silicate minerals

• Quartz (SiO₂): The most common impurity, with high hardness (Mohs 7), needs to be separated by flotation or gravity separation.
• Mica (such as muscovite KAl₂(AlSi₃O₁₀)(OH)₂): Flaky structure, easily mixed with graphite, affecting purity.
• Feldspar (such as potassium feldspar KAlSi₃O₈): Common in weathered deposits.

(2) Iron-containing minerals

• Pyrite (FeS₂): Affects the electrochemical properties of graphite (such as the sulfur content needs to be strictly controlled in battery applications).
• Magnetite (Fe₃O₄): Can be removed by magnetic separation.
• Hematite (Fe₂O₃): Requires acid leaching or reduction roasting.

 

(3) Other common minerals

• Calcite (CaCO₃): easily soluble in acid, can be removed by chemical purification.
• Kaolin (Al₂Si₂O₅(OH)₄): common in cryptocrystalline graphite, reduces the melting point of the ore.
• Rutile (TiO₂): exists in small amounts, affecting stability in high-temperature applications.

 

4. Applications

• Battery industry(Li-ion anodes): High-purity flake graphite (≥99.95%).
• Refractory materials: Graphite crucibles, magnesia-carbon bricks.
• Lubricants: Graphite powder, expanded graphite.
• Nuclear industry: Ultra-pure graphite as a neutron moderator (e.g., in HTGR reactors).

 

5. Global Distribution of Deposits

(1) China (Largest global producer)

• Flake graphite: Heilongjiang (Jixi, Luobei), Shandong (Pingdu), Inner Mongolia (Xinghe).
• Amorphous graphite: Hunan (Chenzhou), Jilin (Panshi).

(2) Other Major Producers

• Brazil: High-quality flake graphite (e.g., Minas Gerais).
• Madagascar: Ultra-high-carbon graphite (>90%).
• India: High-grade amorphous graphite (Tamil Nadu).
• Canada: High-purity graphite (Quebec).
• Russia: Large deposits in Eastern Siberia.

 

Graphite Ore Beneficiation Methods

The beneficiation of graphite ore primarily involves flotation (dominant method), gravity separation (auxiliary), and electrostatic separation (rarely used). The characteristics and applications of these methods are detailed below.

 

1. Flotation (Primary Process)

 

(1) Applicability

Best suited for: Flaky graphite (high crystallinity, strong hydrophobicity).

Secondary use: Amorphous graphite (requires optimized reagent systems).

 

(2) Key Advantages

• Efficient separation: Capable of treating low-grade ores (2%~20% fixed carbon), producing concentrates with 90%~99% carbon content.
• Flake protection: Minimizes flake damage through multi-stage grinding + gentle flotation.
• Mature & reliable: Over 90% of graphite processing plants in China adopt flotation.

 

(3) Typical Flow

Roughing: Quickly discard gangue (removing 80%~90% waste).

Multi-stage cleaning (3~5 stages): Gradually enriches carbon content to ≥95%.

Scavenging: Recovers lost graphite particles from tailings.

 

(4) Key Reagents

Reagent Type	Common Reagents	Function
Collector	Kerosene, diesel, dodecylamine	Enhances graphite hydrophobicity
Frother	MIBC, pine oil	Stabilizes the froth layer
Depressant	Sodium silicate, starch	Inhibits quartz, mica, and other gangue minerals

 

2. Gravity-Flotation Combined Process

 

(1) Applicable Scenarios

Ore composition: Graphite associated with dense minerals (e.g., pyrite, rutile).

Process role: Gravity separation serves as pre-concentration, reducing flotation feed and costs.

 

(2) Typical Flow

Gravity pre-concentration (30%~50% waste removal):

• Shaking table: Separates 0.2~2mm coarse graphite while removing heavy minerals.
• Spiral chute:Processes fine fractions (-0.2mm).

Flotation refinement: Conventional flotation for gravity concentrates.

 

(3) Pros & Cons

Pros: Lowers grinding energy consumption, reduces flotation reagent usage.

Cons: Lower recovery for ultrafine graphite (-0.074mm).

 

3. Electrostatic Separation (Rarely Used)

(1) Principle

Based on conductivity differences between graphite (conductive) and gangue (e.g., quartz, silicates).

 

(2) Limitations & Niche Applications

Limitations	Applicable Conditions (Narrow)
Low throughput (<5t/h)	Final purification of ultra-high-purity graphite (>99%)
Requires ultra-dry environment (<5% humidity)	Combined with flotation/chemical methods for final refining
High energy consumption, complex maintenance	Special applications (e.g., nuclear-grade graphite)

 

(3) Practical Use

Lab/small-scale: Purifies high-value graphite (e.g., battery anode materials).

Industrial case: A Canadian plant elevated carbon content from 99% to 99.9% via electrostatic separation.

 

Comparison & Selection Suggestions of Graphite Ore Beneficiation

 

Method	Capacity	Suitable Ore Type	Carbon Recovery	Cost Efficiency	Adoption Rate in China
Flotation	High (>50t/h)	Flaky/amorphous	85%~95%	★★★★★	>90%
Gravity-Flotation	Medium (20~50t/h)	Graphite with heavy minerals	80%~90%	★★★☆	~5%
Electrostatic Separation	Low (<5t/h)	Ultra-high purity	60%~70%	★★☆	<1%

 

Selection Criteria

• Flaky graphite: Prioritize flotation (preserves flake structure).
• Amorphous graphite: Direct flotation or simple gravity pre-concentration.
• Complex ore (sulfides/iron): Gravity-flotation hybrid.
• Ultra-high purity (>99.9%): Flotation + chemical purification + electrostatic (final step).

 

In general, flotation is the absolute mainstream of graphite beneficiation. Gravity separation can be used as an auxiliary means to optimize the process (gravity-flotation mixed process can improve efficiency, and electrostatic separation is limited to special scenarios. The future development focus is on environmentally friendly reagents, pre-separation technology, and energy-saving processes.