Choosing Between Atomised and Milled Ferrosilicon for Diamond Separation

DMS Powders

Choosing Between Atomised and Milled Ferrosilicon for Diamond Separation

Every decision in the diamond recovery process has an impact on yield and profitability. One of the most crucial is the selection of the ferrosilicon medium used in Dense Media Separation (DMS). While both atomised and milled ferrosilicon can be used in mineral separation circuits, the key lies in choosing the right product for your specific operation. DMS Powders manufactures both types and offers an extensive range of grades tailored to the demands of the diamond processing industry.

DMS Powders:

The Basics: What Makes Ferrosilicon Essential in DMS?

Dense Media Separation is a gravity-based process where crushed ore is mixed into a dense ferrosilicon slurry. Diamonds sink due to their higher density, while waste material floats. Ferrosilicon is the preferred medium because of its:

  • High specific gravity
  • Magnetic properties (for recovery and reuse)
  • Consistent suspension behaviour
  • Chemical and physical stability

A deeper overview of the properties and chemistry of ferrosilicon is available at What is Ferrosilicon?.

The type of ferrosilicon used affects the stability, cut-point sharpness, and economic performance of the entire DMS circuit.

Key Differences Between Atomised and Milled Ferrosilicon

The primary distinction lies in the production method and the resulting particle shape:

Atomised Ferrosilicon

Atomised Ferrosilicon is produced by spraying molten ferrosilicon into a cooling chamber, creating spherical particles. It offers superior flowability, higher bulk density, and is typically used in coal, iron ore, and metal recycling.

 Milled Ferrosilicon

Milled Ferrosilicon is made by crushing ferrosilicon ingots into angular, sharp-edged particles. Its lower viscosity and tighter particle size distribution make it more suitable for diamond recovery operations, where precision and medium stability are paramount.

Both types are available from DMS Powders, each tested to exacting standards to ensure repeatable performance in dense media circuits.

 When to Choose Milled Ferrosilicon

Milled ferrosilicon is typically the better choice for diamond separation because it enables:

  • Sharper cut points for precise density separation
  • Lower medium viscosity, improving pump performance
  • More stable suspensions across multiple cycles
  • Improved magnetic recovery due to its shape and composition

For these reasons, diamond recovery plants, especially those processing finer ore, generally prefer milled ferrosilicon. DMS Powders provides a comprehensive range:

  • 65D – Coarser grade for large particle separations
  • 100D – General-purpose grade for most circuits
  • 150D – Balanced grade widely used in global diamond operations
  • 270D – Finer grade for tight separation control
  • 270F – Extra-fine option with minimal turbulence

To explore these products further, see DMS Powders' Milled Ferrosilicon Range.

DMS Powders

What We Stand For

Our Vision
DMS Powders will continue to be a world class market leader in the production, distribution and marketing of dense media ferrosilicon powders.
Our Mission Elements
  • Profitably maintain our core business through excellence in production, distribution and marketing.
  • Develop and enhance global alliances and external relationships to secure optimal market knowledge and increase strategic and operational flexibility.
  • Empower employees with knowledge and resources to act in accordance with core values.
  • Create industry benefit by providing opportunities for shared technical knowledge and skills.
  • Actively manage and build our portfolio of high-quality assets and services.
  • Continue the drive towards a high-performance organisation, in which every individual accepts responsibility and is rewarded for results.
  • Earn the trust of employees, customers, suppliers, communities and shareholders by being forthright in our communications and consistently delivering on commitments.
Our Values
  • Ethics: Uncompromising honesty, integrity, trust and reliability in our dealings with each other.
  • Excellence: Setting high standards in every aspect of business and continuously striving to outperform them.
  • Prosperity: Pursuance of productivity and effectiveness to create a fair value proposition for shareholders, customers, employees and suppliers.
  • Sustainability: An overriding commitment to safety, environmental responsibility and sustainable development.
Key Principles
Automised FeSi

Coarse, Fine, Cyclone 60, Cyclone 40, DMS 70

Milled FeSi

65D, 100D, 150D, 270D, 270F

DMS Powders

Packaging


Our packaging has been specifically designed for:

Ease of handling

Safety

Product integrity

Durability

Water resistance

When Atomised Ferrosilicon Makes Sense

Though less common in diamond applications, atomised ferrosilicon is favoured in certain scenarios:

  • Plants with high-capacity cyclone circuits
  • Applications requiring higher bulk density
  • Coarse separations with lower sensitivity to turbulence

Atomised ferrosilicon is available in several grades:

  • Coarse – For larger separation tanks
  • Fine – Mid-range applications
  • Cyclone 60 and Cyclone 40 – High-performance grades for cyclone-based separation
  • DMS 70 – High-precision operations where ultra-clean separation is required

Though its spherical particles don’t settle as fast, atomised FeSi can provide excellent recovery rates with the right circuit configuration.

 Economic and Operational Considerations

Aside from separation efficiency, several other factors should influence your decision:

  • Recovery rates – Milled ferrosilicon tends to offer better magnetic recovery and less loss due to its shape
  • Consumption – Atomised FeSi may exhibit slightly higher consumption in some plants
  • Medium stability – Milled FeSi has superior suspension behaviour over multiple cycles
  • Ore characteristics – Fine ore types with heavy clay content tend to benefit from milled FeSi
  • Circuit design – Cyclone vs bath separations require different ferrosilicon grades

In operations where separation precision and reduced losses are critical, milled ferrosilicon remains the preferred medium.

Backed by the Experts in Diamond Processing Media

DMS Powders has supported the diamond industry for decades with consistent, high-performance ferrosilicon products. Our commitment to quality, technical support, and supply chain reliability makes us the trusted ferrosilicon supplier for processors worldwide.

We don’t just supply a product. We work closely with our clients to select the right ferrosilicon grade for their plant specifications, helping improve recovery rates while reducing media consumption and cost per tonne.

Choosing the Right Ferrosilicon Starts with the Right Supplier

Not every DMS circuit is the same, and the wrong choice of ferrosilicon can lead to poor separation results, unnecessary losses, or increased costs. Partnering with DMS Powders ensures that your media is matched to your exact processing requirements.

To discuss your plant needs or request a product recommendation, contact our team today.

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Frequently Asked Questions about Ferrosilicon