See How Your Material Performs Before Investing

The best way to evaluate gravity recovery equipment is to run your actual material through it.

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Assay results can indicate that valuable minerals are present, but they do not always show how the material will behave during concentration. Two samples with similar reported grades may produce very different results depending on particle size, liberation, black-sand content, clay, and the amount of competing heavy minerals.

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Yuba Mining and Machine offers practical demonstration testing using representative customer samples. Bring or ship us a prepared sample, and we can process it through our equipment to observe how well it concentrates, how much material can be rejected, and what type of recovery circuit may be appropriate.

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Rather than relying only on theoretical projections, we allow the material and the equipment to demonstrate what can be achieved.

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What This Testing Is Designed to Show

Our testing service is focused on physical gravity concentration.

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We are not presenting it as a complete laboratory assay, mineralogical study, or crushing and milling program. The purpose is to take a representative, properly prepared sample and determine how it responds to our Low-G Horizontal Centrifuge and Reverse Multi-Helix Spiral equipment.

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Testing can help answer questions such as:

• Does the material respond well to gravity concentration?

• Can the valuable heavy fraction be separated from the lighter material?

• How much can the concentrate volume be reduced?

• Is a single spiral sufficient, or would multiple stages be beneficial?

• Does the material contain large amounts of magnetite or black sand?

• Can visible gold or a high-grade concentrate be produced?

• Would a Cleaner, Finisher, Rougher, centrifuge, or staged circuit be most appropriate?

• What equipment layout may best match the customer’s production goals?

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The test provides practical information that can help guide the next step of the project.

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Send a Representative, Prepared Sample

The quality of the test depends heavily on the quality of the sample.

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The material should represent what the customer expects to process during normal production, not only the richest visible section or a hand-selected concentrate.

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Depending on the project, the sample may consist of:

• Sluice concentrate

• Jig concentrate

• Centrifuge concentrate

• Black-sand concentrate

• Heavy-mineral concentrate

• Fine placer material

• Prepared mine tailings

• Crushed and milled hard-rock material

• Material from an existing cleanup circuit

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Whenever possible, hard-rock samples should arrive already crushed and milled to the size the customer expects to use in production. Gravity equipment cannot recover gold that remains locked inside unbroken or insufficiently milled rock.

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Likewise, clay-rich material should be identified before shipment. If the sample remains bound together in clay or compacted lumps, additional washing or scrubbing may be required before meaningful concentration can occur.
 

How Much Material Should Be Sent?

Most samples range from approximately 25 to 250 kilograms (55 to 550 pounds), depending on the material and what the customer wants the test to determine.

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A smaller sample of around 25 kilograms (55 pounds) may be sufficient to demonstrate final cleanup through the Spiral Finisher. Larger samples are more useful when evaluating concentration ratio, repeatability, staged processing, or the performance of a broader recovery circuit.

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For more complete evaluations, we prefer enough material to operate the equipment under stable conditions rather than feeding only a few scoops. In these cases, a sample closer to 250 kilograms (550 pounds) may provide a more representative demonstration.

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Before shipping material, contact us so we can discuss:

• The type of material

• Where the sample was collected

• How it was prepared

• Its approximate particle size

• Whether it contains clay

• The expected amount of black sand or magnetite

• The customer’s processing objective

• The available sample weight

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This allows us to recommend a practical sample quantity and avoid unnecessary freight expense.

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Our Testing Process

1. Project Discussion

We begin by learning what the customer is trying to accomplish.

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This may include recovering fine gold, reducing a large black-sand concentrate, evaluating historic tailings, selecting equipment for a new plant, or improving an existing recovery circuit.

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We also discuss how the sample was collected and prepared so that the test results can be interpreted properly.

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2. Representative Sample Review

When the material arrives, we review its general condition and suitability for testing.

We look at factors such as:

• Feed size

• Moisture

• Clay or compaction

• Visible black sand

• Heavy-mineral content

• Oversize material

• Feed consistency

• Whether the sample appears adequately prepared

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If the material is not ready for meaningful testing, we will explain what additional preparation may be needed.

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3. Demonstration Through the Equipment

Most testing occurs with the 16-inch Reverse Multi-Helix Spiral Finisher, particularly when the customer provides a prepared concentrate.

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The Finisher is useful for demonstrating how tightly the material can be separated and whether the concentrate can be reduced to visible gold, a smelt-grade product, or a smaller high-grade heavy-mineral fraction.

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Depending on the material and sample quantity, testing may also involve:

• The 16-inch Spiral Cleaner

• A staged Cleaner and Finisher arrangement

• The 24-inch Spiral Rougher

• The Low-G Horizontal Centrifuge

• Multiple passes at different settings

• Broader and tighter separation cuts

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The equipment is adjusted according to how the material responds rather than forcing every sample through one standard setting.

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4. Concentrate Evaluation

After processing, we examine the resulting concentrate and tailings.

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The evaluation may include:

• Approximate feed and concentrate weights

• Concentration ratio

• Visible gold recovery

• Amount of black sand or heavy material retained

• Amount of lighter material rejected

• Concentrate cleanliness

• Whether additional processing stages are beneficial

• Observations about feed preparation and classification

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When enough recoverable material is present, the test may produce visible gold that the customer can inspect directly.

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That is often the most useful demonstration: beginning with a larger volume of concentrate and finishing with gold in hand.

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5. Findings and Recommendations

Following the test, we prepare a brief report summarizing what we observed.

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The report may include:

• Description of the material tested

• Equipment used

• General test procedure

• Concentration results

• Photographs of the feed and final concentrate

• Observations about how the material behaved

• Recommended equipment

• Suggested equipment sequence

• Preliminary plant-layout considerations

• Additional preparation or testing recommendations

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The report is intended to provide practical guidance for equipment selection and process planning. It is not represented as a certified assay or full metallurgical study unless those services are separately arranged through a qualified laboratory.

 

Bring Us Your Material

Do not assume that your concentrate contains too much black sand, that your gold is too fine, or that the material cannot be cleaned further.

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Bring or ship us a representative, properly prepared sample and let us run it through the equipment.

We will evaluate how the material responds, document our observations, and recommend a practical next step based on what the test actually shows.

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