When using borax smelting to extract gold, the formation of granules instead of a fused mass can occur due to several factors. Here are the potential causes and solutions to achieve proper fusion:

### Causes:

1. **Insufficient Heat**:

- Borax acts as a flux and requires high temperatures to properly melt and fuse with the gold. If the temperature is too low, the borax and gold may not fully melt, leading to granule formation.

2. **Incorrect Borax-to-Gold Ratio**:

- Too much or too little borax can affect the melting process. Excess borax can create a viscous slag that traps gold particles, while insufficient borax may not provide enough fluxing action.

3. **Impurities in the Gold**:

- High levels of impurities (e.g., other metals or minerals) can interfere with the melting process, causing the gold to form granules instead of fusing.

4. **Improper Mixing**:

- If the borax and gold are not thoroughly mixed, the fluxing action may be uneven, leading to incomplete fusion.

5. **Rapid Cooling**:

- If the molten mixture cools too quickly, it may solidify into granules instead of forming a homogeneous mass.

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### Solutions:

1. **Increase the Temperature**:

- Ensure the furnace reaches a high enough temperature (typically above 1064°C, the melting point of gold) to fully melt both the gold and borax. Use a high-temperature furnace or torch capable of achieving these temperatures.

2. **Optimize the Borax-to-Gold Ratio**:

- Use an appropriate amount of borax (typically 2-3 times the weight of the gold concentrate) to ensure proper fluxing without creating excessive slag.

3. **Remove Impurities**:

- Pre-treat the gold concentrate to remove as many impurities as possible before smelting. This can include washing, roasting, or using other refining methods.

4. **Thorough Mixing**:

- Ensure the borax and gold concentrate are well-mixed before heating. This promotes even melting and fusion.

5. **Control Cooling**:

- Allow the molten mixture to cool slowly to encourage proper fusion. Rapid cooling can be avoided by insulating the crucible or using a controlled cooling process.

6. **Add a Flux Enhancer**:

- Consider adding a small amount of silica or soda ash to the borax flux to improve its fluidity and ability to fuse with the gold.

7. **Use a Clean Crucible**:

- Ensure the crucible is clean and free of contaminants that could interfere with the melting process.

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By addressing these factors, you should be able to achieve proper fusion and obtain a homogeneous gold button instead of granules.