earth science

Wilfley table

Wilfley table is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Wilfley table rather than just read about it. In short: The Wilfley Table is commonly used for the concentration of heavy minerals from the laboratory up to the industrial scale. It has a traditional shaking (oscillating) table design with a riffled deck.

Key takeaways

Wilfley table belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Wilfley table to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Wilfley table from memory before moving on to harder problems.

Reference excerpt

The Wilfley Table is commonly used for the concentration of heavy minerals from the laboratory up to the industrial scale. It has a traditional shaking (oscillating) table design with a riffled deck. It is one of several brands of wet tables used for the separation and concentration of heavy ore minerals which include the Deister Table and Holman Table, all built to handle either coarse or fine feeds for mineral processing. The Wilfley Table became a design used world-wide due to the fact it significantly increased the recovery of silver, gold and other precious metals. Such was the table's widespread use that it was included in Webster's Dictionary, and has been in constant use by miners and metallurgists since its invention.

Origin The Wilfley Table was conceived by Arthur Wilfley, a mining engineer based in Kokomo, Colorado in the United States. As a silver mine operator, Wilfley spent many years refining his separation table design in order to make the extraction of silver more economic. Rather than using heating processes (smelting) to concentrate the ore, Wilfley had been experimenting on mineral separation by use mineral density contrasts. Wilfley was able to perfect a mechanical solution for the recovery of gold and silver from low-grade ores by means of the Wilfley table. The first Wilfley table was built on a preliminary scale in May 1895. The first full-sized table was used in Wilfley's own mill in Kokomo, in May 1896, while the first table sold for installation was placed in the Puzzle Mill, Breckinridge, Colorado, in August 1896. Patented in 1897, the Wilfley table made mining lower-grade ores profitable. Pulverised ore, suspended in a water solution, was washed across a sloping riffled vibrating table so that metals separated as they drained off. The Wilfley Table was said to have revolutionised ore dressing worldwide and more than 25,000 were in service by the 1930s.

Mineral separation

The Wilfley Table was built to solve a problem common in the recovery of heavy ore minerals; approximately 90% of gold grains, platinum group minerals, sulphides, arsenides/antimonides and tellurides, in source rocks are silt-sized (<0.063 mm (0.0025 in)). Concentration of these minerals requires preconcentration techniques that include recovery of this fraction. Preconcentration may involve any number of methods including jigs, spirals, shaking tables, Knelson concentration, dense media separation, panning and hydroseparation. The Wilfley Table exploits preconcentration on the basis of density to separate minerals. It can recover silt to coarse sand-sized heavy minerals for a broad spectrum of commodities including diamonds, precious and base metals, and uranium.

Design and operation The table, like most shaking tables, consists of a riffled deck with a gentle tilt on a stable support to counteract the table's oscillation. A motor, usually mounted to the side, drives a small arm that shakes the table along its length. The riffles are typically less than 10 mm (0.39 inches) high and cover more than half the table's surface. Varied riffle designs are available for specific applications. The riffles run longitudinally, parallel to the long dimension of the table. The table's shaking motion is parallel to the riffle pattern. Deck construction varies from wood to hard-wearing fiberglass where the riffles are formed as part of the mold. The decks are lined with high coefficient-of-friction materials (linoleum, rubber or plastic), which assists in the mineral recovery process. During operation, a slurry of <2 mm (0.079 inches) sample material consisting of about 25% solids by weight is fed with wash water along the top of the table, perpendicular to the direction of table motion. The table is shaken longitudinally, using a slow forward stroke and a rapid return strike that causes particles to migrate or crawl along the deck parallel to the direction of motion. Particles move diagonally across the deck from the feed end and separate on the table according to size and density. Water flow rate, table tilt angle and intensity of the shaking motion must be properly adjusted for effective mineral recovery. The riffles cause mineral particles to stratify in the protected inter-riffle regions. The finest and heaviest particles are forced to the bottom and the coarsest and lightest particles remain at the top. Particle layers migrate across the riffles with addition of new slurry feed and continued water wash. The riffles are tapered and flatten (disappear) towards the concentrate end of the table. The taper of the riffles causes migrating particles of progressively finer size and higher density to be brought into contact with the flowing film of water that tops the riffles; lighter material is washed away as tailings and middlings. Final concentration takes place in the unriffled region at the end of the deck where the layer of material at this stage is usually only a few particles deep.

Efficiency

Mineral separation is hampered by several factors, with particle size being particularly important. As the slurry feed grainsize increases, the efficiency of separation tends to decrease. Separation efficiency is also affected by the stroke of the table (frequency and length); fine feed requires a higher speed and shorter stroke than a coarse feed. A frequency of 200 to 325 strokes per minute is typical. When Wilfley tables were originally employed to rework tailing dumps, the tables were found to enhance mineral recovery by some 35–40% percent compared to existing processes, though this is not always the case. Optimisation of table setup can have a significant impact on the recovery of ore. Using magnetite as a synthetic ore to test recovery on a Wilfley Table, Mackay et al. (2015) found that an optimised table setup (i.e. table inclination, wash-water flow rate, material feed rate, table speed, stroke amplitude, feed grade and feed density) increased magnetite recovery by a factor of 3.7. The Wilfley table, like any wet table, is one of the most metallurgically efficient forms of gravity concentration, being used to treat the smaller, more difficult flow-streams, and to produce finished concentrates from the products of other forms of gravity system. Additional efficiencies are gained in the treatment of low grade feeds where two or even three decks are stacked one above the other allowing for continuous feeding.

Modern usage

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Wilfley table

Start with the simplest possible case. Write down what Wilfley table claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Wilfley table before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Wilfley table ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Wilfley table

In research: Wilfley table appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Wilfley table in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Wilfley table is common in secondary-school and first-year university syllabi. It links to neighbouring topics Metallurgical processes, Mineral processing, Mining equipment, so understanding it makes those chapters shorter.
In everyday life: Look for Wilfley table outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Wilfley table in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Wilfley table means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Wilfley table out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Wilfley table in simple terms?

The Wilfley Table is commonly used for the concentration of heavy minerals from the laboratory up to the industrial scale. It has a traditional shaking (oscillating) table design with a riffled deck.

Why does Wilfley table matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Wilfley table?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Wilfley table.