For every nugget that makes headlines, there are millions of ounces of gold that go unnoticed, washing out the back of sluice boxes or floating over the lip of a pan. This is “flour gold”—particles so fine they resemble dust. In many geological deposits, particularly glacial tills and downstream placers, flour gold represents 90% to 95% of the total value in the ground. Yet, for inexperienced miners and prospectors, it is the most frustrating material to process.

The problem is physics. While gold is dense (Specific Gravity 19.3), flour gold particles are so small and flat that surface tension can make them float like a dry leaf on a pond. When this happens, the gold is lost, returning to the riverbed along with the miner’s potential profits. Recovering this “ghost gold” requires a shift in strategy. It demands precise classification, the chemical alteration of water tension, and fine-tuned mechanical separation. This guide outlines the definitive methods for capturing the microscopic wealth that others leave behind.

Last Updated: January 2025 | Estimated Reading Time: 16 Minutes

Table of Contents

• What is Flour Gold?
• Understanding the Enemy: Why Flour Gold Floats
• Step 1: The Power of Classification
• Step 2: Breaking the Tension (Surfactants)
• Step 3: Panning Techniques for Micro-Gold
• Step 4: Industrial Solutions – Scaling Up with ZONEDING
• Essential Tips for Commercial Success
• Frequently Asked Questions
• Conclusion

What is Flour Gold?

Before attempting to recover it, a miner must first identify exactly what “flour gold” is. In the mining industry, flour gold (also known as “gold dust” or “flood gold”) refers to extremely fine particles of gold handled in bulk. Unlike nuggets or “pickers”—which can be easily moved with fingers or tweezers—flour gold is microscopic, often resembling the texture of baking flour or fine face powder.

The Technical Definition

Geologically, flour gold is not a distinct type of element; it is simply chemically pure gold that has been pulverized by glacial action or eroded over millennia of river transport. In technical processing terms, it is defined by its ability to pass through specific mesh screens.

• Mesh Size: Flour gold typically refers to material that passes through a 40-mesh screen (openings of 0.42mm) and can go as fine as 400-mesh (37 microns).
• Visibility: While a massive pile of flour gold glitters unmistakably, individual particles are often barely visible to the naked eye without the aid of a jeweler’s loupe or strong sunlight.

Understanding the Enemy: Why Flour Gold Floats

To catch flour gold, one must first understand why it behaves differently than a nugget. Gravity separation relies on the principle that gold is 19 times heavier than water and roughly 7 times heavier than the surrounding gravel. In a vacuum, a piece of gold will always drop faster than a piece of quartz.

However, mining does not happen in a vacuum; it happens in water.

• Surface Area to Mass Ratio: As a particle of gold gets smaller, its mass decreases faster than its surface area. Flour gold is often flattened by geological pressure. This flat shape acts like a sail or a wing.
• Surface Tension: Water molecules cling together tightest at the surface. Tiny, dry specs of gold can rest on this “skin” of the water. Even though the gold is heavy, the surface tension is strong enough to support its negligible weight.
• Oil and Grease: Human skin oils, sunblock, or clay residues can coat the gold, making it hydrophobic (water-repelling). This exacerbates the floating effect.

If a miner sees gold dust floating in the corner of their pan, it is not an illusion. It is a physics failure that requires immediate correction.

Step 1: The Power of Classification

The single biggest mistake in fine gold recovery is skipping classification. Classification is the process of separating material by size using screens or sieves.

The Physics of Bed Liquefaction

In a sluice box or a pan, gold sinks because the material is agitated, allowing heavy particles to migrate to the bottom. If a miner tries to process fine dust alongside large rocks (e.g., walnut-sized gravel), the large rocks create turbulence. This turbulence acts like a violent storm, kicking the tiny gold particles back up into the water flow where they are washed away.

The Solution: Screen it Down

To catch flour gold, the feed material must be screened to a uniform size.

• #4 Mesh (approx. 5mm): Remove all larger gravel.
• #8 or #10 Mesh: This is the standard for general sluicing.
• #20 Mesh or #50 Mesh: For dedicated flour gold cleanup.

When material is screened to #50 mesh (roughly the size of table salt), the water flow can be reduced drastically. Low-pressure, laminar water flow allows the tiny gold particles to settle without being blasted out by the turbulence of larger rocks.

Step 2: Breaking the Tension (Surfactants)

When processing concentrates—the black sand and gold mix left at the end of the day—surface tension is the enemy. This is where modern chemistry aids ancient mining.

The “Jet Dry” Method

“Jet Dry” is a brand name for a rinse aid used in dishwashers to prevent water spots. Technically, it is a surfactant (surface active agent). Prospectors have adopted it as a secret weapon.

• How it Works: Surfactants weaken the hydrogen bonds between water molecules. This drastically reduces the surface tension.
• The Effect: When a drop of surfactant is added to the panning tub, the “skin” on top of the water breaks. Any gold dust floating on the surface instantly loses its support and drops to the bottom of the pan like a stone.

Dosage and Application

• In the Panning Tub: Add 3-5 drops of liquid dish soap or a rinse aid like Jet Dry to the tub. Stir gently. The water should feel “wetter” or slippery.
• In the Recirculation System: For home cleanup systems (like a Miller Table or spiral wheel), adding a capful of surfactant to the reservoir ensures that gold dropped onto the table is immediately wetted and sinks into the capture grooves.

Step 3: Panning Techniques for Micro-Gold

Panning for nuggets involves aggressive shaking to get the big rocks out. Panning for flour gold is a delicate art that resembles surgery more than excavation.

The Safety Pan

When finishing a batch of fine concentrates, never pan directly into the river. Always pan into a “safety tub” or a larger plastic bin. This catches any accidents. If the gold is lost from the pan, it remains in the tub to be processed again later.

The “Tap and Swirl”

• Stratification: Shake the pan vigorously side-to-side (not circular) to ensure every speck of gold is at the absolute bottom.
• Angle: Tilt the pan forward slightly more than usual.
• The Wash: Instead of pouring water out, use a gentle circular motion to let the water lap over the edge, carrying only the lightest top layer of black sand.
• The Tap: If the black sand is heavy and packs down, tap the side of the pan with a rubber mallet or the heel of the hand. This vibration keeps the sand fluidized but allows the heavier gold to stay planted.

Step 4: Industrial Solutions – Scaling Up with ZONEDING

While panning is excellent for testing and final cleanup of small batches, it captures zero income. To make money from flour gold, miners need continuous throughput. This requires specialized industrial equipment designed to mimic the physics of the pan but at 100 times the speed.

Sluice Box Matting: Carpet vs. Technology

Old-school miners used carpet or “miner’s moss.” While effective for coarse gold, these mats often pack up with black sand, creating a smooth surface that flour gold slides right over.

• Modern Solution: Vortex Mats or drop-riffle sluices are preferred. These create low-pressure zones (eddies) behind the riffle where fine gold can hide from the main force of the water current.

The Centrifugal Concentrator: G-Force Separation

For commercial operations aiming to recover micron-sized gold (-100 mesh), gravity alone is often too slow. The solution is to artificially increase gravity.

ZONEDING Centrifugal Concentrators (similar to Knelson or Falcon concentrators) spin the ore slurry at high speeds, generating 60G to 80G of force.

• Mechanism: The heavy gold particles are pinned against the ribbed wall of a spinning cone by centrifugal force. Lighter sand and rock are flushed out the top.
• Efficiency: This technology is capable of recovering gold particles as small as 20 microns that would inevitably be lost in a standard sluice box. It is the industry standard for scavenging fine gold from ball mill discharge.

The Shaking Table: The Ultimate Finisher

Once a miner has reduced tons of river gravel down to a bucket of black sand and flour gold, the final separation occurs on a Shaking Table.

• The ZONEDING 6-S Shaking Table: This machine utilizes a flat, riffled deck that vibrates back and forth. Water washes across the table significantly. The vibration separates particles by specific gravity with surgical precision.
• Th Visualization: A distinct yellow line of pure gold separates from the black sand, traveling to the collection launder. It is the only gravity method that acts as a true alternative to chemical leaching for fine cleanups.

Feature	Sluice Box	Centrifugal Concentrator	Shaking Table
G-Force	1 G	60 – 80 G	1 G + Vibration
Feed Size	Coarse to Fine	Fine (< 2mm)	Fine (< 2mm)
Recovery Size	> 50 mesh	> 400 mesh (Micron)	> 200 mesh
Primary Use	High Volume / Roughing	Scavenging Fines	Final Cleanup / Upgrade

Essential Tips for Commercial Success

1. Water Flow Management

The most common error in running fine gold equipment (like the ZONEDING Spiral Chute or Shaking Table) is using too much water. Fine gold is easily blown away. The water should be a thin film, barely covering the sand. If the water is turbulent or “white,” it is too fast.

2. Clay is the Enemy

Clay creates a thick, viscous slurry that holds onto gold particles, preventing them from sinking. If the deposit has heavy clay, a Log Washer or Trommel Scrubber is mandatory before the material ever hits the recovery circuit. These machines scrub the rocks, dissolving the clay into a liquid that can be washed away, leaving the gold free to settle.

3. Avoid Mercury

Historically, miners used mercury (amalgamation) to catch flour gold because mercury binds to gold on contact.

• The Reality: Mercury is toxic, illegal in many jurisdictions, and destroys the environment.
• The Alternative: Modern shaking tables and centrifugal concentrators achieve similar or better recovery rates (95%+) without the legal and health risks associated with mercury.

Frequently Asked Questions

• Q1: What is the smallest size of gold that can be recovered by gravity?
• With standard panning, recovering gold smaller than 100 mesh is difficult. However, with Centrifugal Concentrators, mining operations can recover gold particles down to 10-20 microns. At this size, the gold is like paint powder, but it still holds significant value in volume.
• Q2: Does “magnet fishing” help with flour gold?
• Yes, but indirectly. Flour gold is often mixed with heavy black sands (Magnetite). By using a powerful magnet to remove the magnetic iron sand, a prospector effectively “shrinks the haystack,” making it easier to find the gold needles. Note: Always check the magnet tailings, as gold can sometimes get trapped between magnetic particles.
• Q3: Why use a spiral concentrator?
• A spiral concentrator (or spiral chute) is an excellent, low-energy tool for processing large volumes of fine material. It uses gravity and centrifugal force as the slurry flows down a corkscrew channel. ZONEDING manufactures fiberglass spirals that are ideal for pre-concentrating heavy minerals before they are sent to a shaking table.

Conclusion

Catching flour gold is not about luck; it is about engineering. The miner who relies solely on a shovel and a hopeful attitude will leave the majority of their wealth in the tailings pile.

The path to profitability in fine gold recovery follows a strict hierarchy:

• Classify material to a uniform size so turbulence doesn’t rob the catch.
• Consolidate fines using surfactants to break surface tension in the finishing stage.
• Centrifuge bulk material to capture the micron-gold that gravity sluices miss.
• Concentrate the final product using precision tables.

Why Choose ZONEDING for Fine Gold Recovery?
ZONEDING understands that in modern mining, the profit is in the details. The days of stumbling upon fist-sized nuggets are largely over. Today’s mine is a factory that processes volume. ZONEDING provides the complete flowchart—from Trommel Screens for washing clay to High-G Centrifuges and 6-S Shaking Tables for final capture.

Stop letting the river take your salary.

Contact ZONEDING today to design a fine gold recovery circuit that turns dust into deliverable bars.

Last Updated: January 2026