Magnesium Oxide Cupel

Magnesium Oxide Cupel
Magnesium Oxide Cupel is a high-purity refractory container designed for use in fire assay and precious metal analysis. Made from dense magnesium oxide, it can withstand extreme temperatures without cracking or deforming, ensuring accurate and consistent melting and refining of samples. Its excellent thermal stability and resistance to chemical corrosion make it suitable for use with gold, silver, and other noble metals. The cupel effectively absorbs oxidized impurities during the assay process, maintaining clean separation and reliable analytical results. We can supply high-quality magnesium oxide cupels with various specifications and competitive prices, offering customized solutions to meet specific requirements.
Or email us at sales@heegermaterials.com.Magnesium Oxide Cupel Data Sheet
| Color | Yellow, Light yellow, or White |
| Materials | MgO |
| Purity | 96% min |
Magnesium Oxide Cupel Description
Magnesium Oxide Cupel is produced from premium-grade raw materials with a unique formulation containing about 96% magnesium oxide and 4% fluxing agents. This composition allows it to absorb more lead oxide than traditional bone ash cupels, resulting in excellent porosity, mechanical strength, and consistent performance. During fire assay and cupellation, the cupel effectively absorbs lead oxide without splashing, leaving behind high-purity gold and silver alloy grains. It maintains structural integrity without cracking or pitting at high temperatures and remains unaffected by humidity or freezing conditions. After use, the precious metal grains can be easily separated from the cupel surface.
Magnesium Oxide Cupel Specifications
| Type | Height(H) mm | Top OD(D) mm | Bottom OD(D2) mm | Top ID(D1) mm | Inner Depth(H1) mm | Height of Ridge(H2) mm |
| 2X | 17 | 24 | 19 | 18 | 8 | 4.5 |
| 3 | 20 | 26 | 20 | 23 | 5.5 | 8 |
| 4A | 22 | 27 | 20 | 24 | 6 | 7.5 |
| 4 | 22 | 29 | 23 | 24 | 6 | 8 |
| 5 | 26 | 35 | 26 | 27 | 8 | 6.5 |
| 6A-26 | 26 | 40 | 30 | 31.2 | 11.8 | 6 |
| 6A-29 | 29 | 40 | 30 | 31.2 | 11.8 | 9 |
| 7A | 32 | 40 | 30 | 31.2 | 11.8 | 12 |
| 7AS(7X) | 35 | 40 | 30 | 31.2 | 11.8 | 15 |
| 7AS-15 | 32 | 40 | 30 | 32 | 15 | 12 |
| 8 | 27.1 | 44.3 | 34.6 | 34.2 | 8.5 | 9 |
| 8A | 35 | 45 | 37 | 38 | 13 | 13 |
| 8AM | 35 | 45 | 37 | 33 | 12 | 15 |
| 8S | 40 | 44 | 34 | 38 | 14 | 13 |
| 9 | 30 | 51 | 43 | 40 | 11 | 5 |
| 9A | 34 | 39 | 15 | 14 | ||
| 10 | 30.2 | 60 | 49.7 | 52.6 | 11.5 | 11 |
| 11 | 44 | 56.8 | 48.8 | 47.8 | 14.8 | 10 |
| 14 | 70 | 110 | 88 | 80 | 24 | 14 |
Magnesium Oxide Cupel Features
- Premium Raw Materials and Advanced Formulation: Made with high-purity magnesium oxide and precise additives to ensure optimal absorption and consistency in every batch.
- Smooth Surface and Uniform Quality: Each cupel has a dense, even texture with a clean finish, ensuring accurate and repeatable fire assay results.
- Strong Mechanical and Thermal Stability: Maintains structural integrity under high temperatures with excellent resistance to cracking, pitting, and thermal shock.
- Weather-Resistant Performance: Unaffected by humidity or freezing conditions, allowing long-term storage without degradation in quality.
- Efficient Lead Oxide Absorption: Capable of rapidly absorbing a large proportion of lead oxide during cupellation, ensuring high recovery rates of gold and silver.
- Environmentally Safe and Reliable: Free from lead contamination, ensuring clean processing and minimal loss of precious metals.
- Precision Manufacturing and Quality Control: Produced with modern machinery under ISO 9001-certified systems, guaranteeing consistent performance and dimensional accuracy.
- Customizable Options: Heeger Materials (HM) provides high-quality Magnesium Oxide Cupels available in various sizes and specifications, with custom solutions to meet specific testing needs.
Magnesium Oxide Cupel Applications
- Fire Assay Analysis: Used in laboratories for determining precious metal content in ores, concentrates, and alloys through the cupellation process.
- Gold and Silver Refining: Efficiently separates precious metals from lead and other impurities, ensuring accurate recovery of high-purity gold and silver.
- Mining and Metallurgical Testing: Essential for quality control and assay testing in mining operations, smelting plants, and metal refining facilities.
- Analytical Laboratories: Applied in research and testing institutions for reliable quantitative analysis of noble metals.
- Industrial Quality Assurance: Used in production environments where precise metal content verification is required for raw materials and finished products.
Magnesium Oxide Material Properties
Magnesium Oxide Ceramic Machining

Magnesium oxide can be machined in green or bisque form before sintering, and to a limited extent in its fully sintered state. In its pre-sintered state, the material is relatively soft and easier to shape, but like many ceramics, it undergoes significant shrinkage—up to 20%—during sintering, which can affect final dimensions. Fully sintered magnesium oxide is very hard and brittle, requiring diamond tools and precision equipment for any post-sintering machining.
Machining Methods and Considerations
- Green or Bisque Machining: Easier to cut and form, suitable for complex shapes before firing.
- Sintering Shrinkage: Expect about 15–20% dimensional reduction during sintering, which impacts tolerance control.
- Post-Sintering Machining: Requires diamond grinding tools due to the material’s hardness and brittleness.
- Fragility: Fully sintered MgO is prone to chipping and fracture if not handled with care during machining.
- Tooling and Time: Machining dense MgO ceramics is time-consuming and requires specialized equipment.
Magnesium Oxide Ceramic Packaging
Magnesium oxide ceramic products are typically packaged in vacuum-sealed bags to prevent moisture or contamination and wrapped with foam to cushion vibrations and impacts during transport, ensuring the quality of products in their original condition.

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