Midwest Refineries – Precious Metal Refiners & Gold Buyers
Precious Metal Processing, Refining and Assaying
Gold, Silver, Palladium, Rhodium, & Platinum Assaying and Refining in the USA.
- Over 85 Years in Business
- Serving All Of The USA
- 4418 Florida National Dr., Lakeland, FL. 33813
Gold jewelry, dental scrap, and other gold items.
Silver jewelry, utensils, medical scrap & more!
Jewelry, flake, bars, scrap and many other items.
Other Precious Metals
Palladium, Rhodium and other precious metals.
How We Determine What Your Precious Metals Are Worth — and Why It Matters
When you ship gold, silver, platinum, palladium, or rhodium to a refinery, you’re trusting that company to measure your metal accurately and pay you accordingly. The assay — the determination of your metal’s exact purity and content — is the foundation of your entire settlement. Get it wrong, and you get paid less than you deserve.
At Midwest Refineries, we have operated a modern assay laboratory for over 85 years. We use the most appropriate testing method for every type of metal and every order size, from a single gold ring to large industrial lots of platinum thermocouple wire. Our commitment is simple: your metal is measured correctly, and you are paid correctly.
This page explains exactly how we evaluate your precious metals and why our methods give you the most accurate — and therefore the most favorable — results.
Have Questions About Your Specific Metal?
Call us before you ship — we’ll explain how your material will be tested and what to expect.
Why Accurate Assaying Directly Affects Your Payout
Precious metal refining is not like selling a used car or trading in jewelry at a pawn shop. The payout you receive is calculated directly from a laboratory measurement of what your metal actually contains. An inaccurate assay — whether through imprecise methods, inadequate equipment, or deliberate undervaluation — costs you money.
- The difference between an accurate and inaccurate assay can be significant.
On a 10-ounce gold lot at current market prices, even a 1% discrepancy in measured purity represents a meaningful dollar difference. On large platinum or palladium shipments, where multi-metal assays determine how much of each element is present, precision matters even more. This is why we invest in proper laboratory equipment and trained staff — not because it’s required, but because it’s the right way to treat customers.
From Shipment to Settlement: How Your Metal Is Processed
Your shipment arrives at our secure Lakeland, Florida facility and is logged and weighed upon receipt.
We determine the appropriate assay method based on the metal type and quantity in your shipment.
For orders above the melt threshold (3 troy oz. for gold and platinum; 10 troy oz. for silver), your material is smelted and a precise sample is taken for laboratory analysis.
We perform fire assay, ICP-OES, XRF, or direct purchase evaluation as appropriate to your material.
You receive a settlement report showing the exact metal content determined, the spot price used, and your payout calculation.
You choose your settlement: check, bank wire, or exchange for precious metal coins or bars.
Ready to Ship Your Precious Metals?
Contact us first — we’ll confirm what you have, how we’ll test it, and what you can expect to receive. Our assay laboratory and our 85-year reputation exist for one purpose: to make sure you are paid honestly and accurately for every precious metal you send us. If you have questions about how your specific material will be evaluated, call us. We’re always happy to walk you through it.
4418 Florida National Dr., Lakeland, FL 33813
Gold • Silver • Platinum • Palladium • Rhodium | Family-owned since 1939 | Serving all of the USA
FAQs About The Testing Methods We Use — and When We Use Each One
Fire Assay
The Most Accurate Method for Gold – Fire assay is the oldest known method of assaying gold and remains the most accurate. The name sounds dramatic, but the process is precise science developed over millennia.
When gold is melted, we take a carefully weighed sample — either by drilling through the poured bar or by capillary tube sampling while the metal is molten. That sample is wrapped in assay lead foil along with a quantity of pure silver, then placed in a furnace inside a cupel, a specially designed disposable crucible. At high temperature, all non-precious metals are absorbed into the hot cupel. What remains is a small button of precious metal.
That button is removed, brushed clean, hammered flat, rolled thin, and then heated in a porcelain crucible with a weak nitric acid solution. The acid dissolves and removes the silver, which is recovered from the solution. The remaining gold is rinsed in distilled water to remove any residual acid, then dried and weighed again with precision scales.
The result: a gold sample that is at least 99.999% pure. The ratio of the final pure weight to the original sample weight gives us the exact assay — a precise percentage of gold content that forms the basis of your settlement. For platinum group metals, the same initial process is followed, but final elemental readings are done using ICP-OES.
ICP-OES
Multi-Element Analysis for Platinum Group Metals: Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) is the standard technique for precise elemental analysis of platinum, palladium, and rhodium. It is particularly valuable when a material contains multiple precious metals and each needs to be measured separately and accurately.
The sample, typically prepared by dissolving a solid specimen, is mixed with water and introduced into a high-temperature plasma torch. Atoms in the plasma emit light at specific wavelengths that are unique to each element. An optical spectrometer reads those wavelengths, and when calibrated against known standards, the result is a quantitative breakdown of every element present in the sample.
This is how we accurately determine palladium and rhodium content in platinum alloys and mixed scrap — content that you deserve to be paid for, and that less thorough refiners may simply ignore or bundle into a single imprecise platinum reading.
XRF (X-Ray Fluorescence)
X-Ray Fluorescence spectrometry allows us to identify elements in solid, powdered, and liquid samples without destroying the material. The spectrometer irradiates the sample with X-rays and measures the fluorescent emission wavelengths produced — each element has a characteristic signature.
XRF is fast and non-destructive, which makes it excellent for preliminary screening and identification. We use it to quickly evaluate incoming materials, confirm what metals are present, and determine what further testing is appropriate. It is a valuable diagnostic tool, though for final settlement purposes we rely on fire assay and ICP-OES for the highest accuracy.
Electronic Testing and Touchstone Methods
Used for Small Lots and Quick Identification: For smaller orders — a gold ring, a few dental crowns, a piece of jewelry — a full melt and laboratory assay is not always necessary. Our trained staff can accurately determine the purity of most precious metals using electronic testing equipment or the traditional touchstone method.
The touchstone is a smooth, fine-grained black stone (usually quartz or jasper) that has been used to test gold since at least 500 BC. An unknown piece is rubbed against the stone alongside gold needles of known karat values. The resulting marks are compared and treated with acid to reveal color reactions that indicate karat content. When nitric acid is applied to 10K gold, it turns reddish-brown. 14K gold does not change color. 18K to 24K gold stays bright on the stone. Electronic gold testers can also provide a good baseline karat reading, though neither method approaches the accuracy of a fire assay for large-lot settlement purposes.
For silver identification: filing a deep notch in an item and applying acid will reveal whether it’s sterling silver (which turns an ashy light gray) or silver-plated copper (which bubbles green as the acid reacts with the copper underneath).
These methods allow us to purchase small lots outright — quickly and fairly — without requiring a full melt and assay, which is a service we’re proud to offer customers who have just a few items to sell.
Assay Method Quick Reference
Best Used For: Gold; platinum group metals (used alongside ICP)
Accuracy Level: Extremely high — 99.999%+ purity achieved in sample
Notes: Oldest known method, still considered the gold standard
Best Used For: (Inductively Coupled Plasma) – Platinum group metals; multi-element analysis
Accuracy Level: Very high; quantifies multiple elements simultaneously
Notes: Used for platinum, palladium, rhodium; typically follows fire assay sample prep
Best Used For: (X-Ray Fluorescence) – Non-destructive screening; solid samples
Accuracy Level: Good for identification; less precise than fire assay for final settlement
Notes: Quick, non-destructive; used for screening and preliminary evaluation
Best Used For: Small lots; quick karat identification
Accuracy Level: Useful for sorting; not sufficient for final precious metal settlement
Notes: Used with small orders where full melt and assay is not required
Best Used For: Field identification; small gold items
Accuracy Level: Approximate; confirms karat range but not fine purity
Notes: Technique dating to 500 BC; still useful for preliminary identification
Our Commitment: You Are Paid for Every Milligram You Send
The reason Midwest Refineries has maintained loyal repeat customers for over 85 years is not complicated: we measure accurately, we pay fairly, and we don’t hide fees. The assay lab is where that promise is kept.
Every precious metal shipment we receive is handled with the same care, whether it’s a single gold crown or a 40-ounce lot of platinum thermocouple wire. We match the assay method to the material, document the results, and base your settlement entirely on what the laboratory finds — nothing more, nothing less.
We also recover and pay on every metal present in mixed scrap. If your platinum thermocouple wire contains palladium and rhodium, we find it and pay you for it. If your gold lot contains silver, we account for it. You deserve every dollar your material contains, and our laboratory is built to find it.
Gold jewelry, dental scrap, and other gold items.
Silver jewelry, utensils, medical scrap & more!
Jewelry, flake, bars, scrap and many other items.
Other Precious Metals
Palladium, Rhodium and other precious metals.