Dental Gold Assay Process: How Dental Gold Is Tested and Valued
A crown's colour and weight cannot tell you how much gold it contains. A dental gold assay measures it. This guide explains what an assay is, how the testing works, what XRF and laboratory fire assay can and cannot tell you, and how a measured gold percentage becomes an offer, for individual sellers and dental practices alike.
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A dental gold assay is the measurement of what a lot of dental metal is actually made of: which elements are present and what percentage of the metal each one represents. It matters because crowns, bridges, inlays and onlays are cast from many different alloys, and colour, weight and age cannot tell you the gold content of any of them. The assay result, the gold percentage, is multiplied by the weight of metal to give the gold content. The evaluation considers the composition of the dental alloy, its verified precious metal content and the applicable valuation terms, and the written report sets out the figures used.
- Dental alloys range from high-gold castings to palladium-based "white" alloys to base metals with no gold at all. Two crowns that look identical can test very differently.
- The common test methods are X-ray fluorescence (XRF) and laboratory assay on a prepared sample. Each measures a sample, so how the sample is prepared matters as much as the instrument.
- Porcelain, cement and tooth structure add weight but contain no gold. The weight that counts is the weight of metal, not the weight of the restoration as it arrives.
- At Dental Gold Experts, everything you submit is melted together as one lot and Blake analyzes multiple spots on the melted material by XRF to determine its gold content. Your written report shows the weight, the gold percentage, the gold spot price used, the payout rate and the payout calculation.
To see how weight and purity change the figure before you send anything, use the dental gold value calculator. The final offer is determined after melting and assay.
What Is a Dental Gold Assay?
An assay is a measurement of composition. A dental gold assay answers three questions about a quantity of dental metal: which metals are in it, what proportion of the metal each one makes up, and therefore how much gold it contains. The result is a measured percentage, not an opinion formed by looking at the pieces.
The reason dental gold needs this is that it is not made to a stated purity. Jewelry is usually manufactured to a karat standard and marked with it; a dental crown is cast by a laboratory from whichever alloy suited the clinical job, and that alloy is chosen for how it casts, fits, wears and bonds to porcelain rather than for its gold figure. The alloy is rarely marked on the finished restoration, so the only way to know what a particular lot contains is to measure it.
Three ideas run through everything that follows, and keeping them separate avoids most of the confusion around dental gold value:
- Gross received weight is what the material weighs when it arrives: metal plus porcelain, cement, tooth structure and anything else attached.
- Metal weight is the weight of the metal alone, once non-metal material has been removed and the lot has been melted. This is the weight a dental gold assay percentage is applied to.
- Gold content is metal weight multiplied by the measured gold percentage. It is the central quantity in a dental gold valuation.
Why Dental Gold Cannot Be Valued by Looking at It
The dental profession classifies casting alloys by their noble-metal content, not by colour or karat. The American Dental Association's materials for indirect restorations resource reproduces the ADA Council on Scientific Affairs' 2003 classification: high noble alloys contain at least 60% gold and platinum-group metals with gold making up at least 40%; noble alloys contain at least 25% gold and platinum-group metals; predominantly base alloys contain less than 25%. The same page notes that the current standard for these materials is ANSI/ADA Standard No. 134 / ISO 22674, and that the classification itself is archived reference material.
| ADA class (2003) | Requirement | What it does not tell you |
|---|---|---|
| High noble | Gold + platinum-group metals ≥ 60%, gold ≥ 40% | The actual gold figure. It must be at least 40%; it may be far higher |
| Noble | Gold + platinum-group metals ≥ 25% | Whether gold is present at all. The noble content can be mostly palladium |
| Predominantly base | Gold + platinum-group metals < 25% | Whether there is any gold. There may be little or none |
Source: ADA, "Materials for indirect restorations" (archived classification, for information only). The classes are minimum requirements an alloy must meet to carry the label. They are not the measured composition of any particular restoration, which is what a dental gold assay provides.
Three consequences follow. A yellow crown may sit anywhere in the high-noble range or be a lower-gold alloy with a warm colour. A silver-coloured or "white" restoration may be a palladium-based noble alloy that still contains gold, or a nickel-chromium or cobalt-chromium base-metal casting that contains none; our guide to white dental gold covers the difference. And a porcelain-fused-to-metal crown hides its metal coping under ceramic entirely, so there is nothing to judge by eye.
Appearance narrows the possibilities; a dental gold assay settles them. If you are trying to decide whether a piece is worth sending at all, how to identify dental gold covers the practical signs, and you can send pieces you are unsure about: the evaluation considers verified precious metal content, and base metal pieces add none.
How the Dental Gold Assay Process Works, Step by Step
Facilities differ in their equipment and their paperwork, but any evaluation that ends in a measured gold figure passes through the same stages. Where this guide describes what Dental Gold Experts does, it says so; the rest describes the process in general. The step-by-step account of our own method is on how we assay dental gold.
1. Receiving and sorting the material
The package is opened and the contents identified. A typical lot is mixed: full-cast crowns, porcelain-fused-to-metal units with ceramic still bonded, bridge spans, inlays, perhaps pieces still cemented to extracted teeth. At Dental Gold Experts, we sort your material, and non-metal material is removed as part of the melting process. You do not need to do this yourself, and you should not try to burn, grind or chemically strip restorations at home.
2. Weighing
Weight enters the calculation twice: the weight of what arrived and the weight of the metal that is actually valued. A gross received weight is a useful reference, but it is not the figure the dental gold assay percentage is applied to; that is the weight of metal after melting. At Dental Gold Experts, payout calculations use the post-melt weight. If it is practical, weigh and photograph your material before shipping and keep a simple log; Dental Gold Experts does not currently require this, but it gives you your own reference.
3. Melting the lot
Melting combines every piece into one uniform metal, so there is a single composition to measure instead of dozens, and a weight that belongs to the whole lot rather than to one piece. Dental Gold Experts melts everything a customer submits together, as one lot. Melting is irreversible, which is why material cannot afterwards be returned in its original form.
4. Analyzing the melted metal
Blake analyzes multiple spots on the melted material by XRF to determine its gold content. XRF, explained in the next section, reports the elements present and their proportions; the figure carried forward is the gold percentage of the lot. Other facilities use other analytical methods, compared below.
5. Calculating gold content and value
With the dental gold assay result in hand, the arithmetic is short. Metal weight × gold percentage = gold content. Gold content ÷ 31.1035 converts grams to troy ounces (the National Institute of Standards and Technology lists the troy ounce as 31.10348 g in its Guide to the SI, Appendix B.9), and troy ounces × a gold price = the value of the contained gold. The offer is that value multiplied by a payout rate. At Dental Gold Experts, your offer is calculated from the post-melt weight, the gold percentage, the gold spot price shown in your written report, and the payout rate.
6. Written report and offer
The result of a dental gold assay should be a document, not a verbal number. Dental Gold Experts' written report shows the weight, the gold percentage, the gold spot price used, the payout rate and the payout calculation, so every step from metal to money can be followed. If you accept, payment is issued within 24 hours after acceptance, usually immediately, by Zelle, PayPal, check or ACH bank transfer; receipt depends on the payment method.
The question I am really answering with a dental gold assay is not "is this gold?" but "how much of this is gold?" Those are different questions. A bag of crowns can be half high-gold castings and half base metal, and until it has been melted into one lot and the melted metal read in several places, any number attached to it is a guess. The written report exists so that you do not have to take my word for the result.
XRF Testing vs. Fire Assay and Other Laboratory Methods
Two families of method come up whenever a dental gold assay is discussed, and they are often presented as rivals. They are better understood as different tools, each only as good as the sample it is given.
X-ray fluorescence (XRF)
An XRF instrument directs X-rays at the sample. Each element in the sample responds by emitting X-rays of its own at energies characteristic of that element, and a detector reads those energies and their intensities to report which elements are present and in what proportion. XRF itself does not consume or alter the sample, and it reports several elements at once, which is why it suits gold alloys that also contain platinum, palladium, silver and copper.
Its defining limitation is depth. XRF reads a thin layer near the surface of a sample, and on dense gold alloys that layer is on the order of tens of micrometres (XRF analysis depth on metals, instrument-maker explainer). Pointed at an unmelted crown, it reports that spot on that crown's surface: a gold-coloured plating can read as gold, a porcelain-fused unit offers almost no metal to read, and one piece cannot stand for a mixed lot.
Pointed at a melted, homogeneous sample, the same layer is representative of the whole. The difference between XRF as a rough check and XRF as the measurement behind a dental gold assay is sample preparation, not the instrument.
Fire assay (cupellation) and other laboratory methods
Fire assay is the classical laboratory method for gold: a weighed portion of the sample is fused with lead, the lead and base-metal oxides are absorbed by a porous cupel, and the bead of gold and silver that remains is separated and weighed. It is the method standardised for gold bullion in ASTM E1335 (whose methods span 0.5–4% and 20–99.8% gold and assume "trained assayers capable of performing common fire assay procedures skillfully and safely"), and for jewellery and precious-metal alloys in ISO 11426, which specifies the method "for the determination of gold on a material considered homogeneous".
It is destructive of the portion tested, slow, and performed by specialist laboratories, which also use instrumental methods on dissolved samples. It is not Dental Gold Experts' method: our measurement is XRF on the melted lot.
Two points in those standards matter more than the method's reputation. Both assume a homogeneous sample, which for mixed dental scrap means melting first, exactly as with XRF; and both are written for bullion and jewellery alloys, so a laboratory certificate is only as meaningful as the sample it describes. The same applies to trade standards sometimes quoted in this context: the London Bullion Market Association's Good Delivery List concerns refiners' gold and silver bars for settlement in the London market ("no other refined gold or silver products … fall within the scope"), and says nothing about how a dental scrap buyer tests crowns.
| Method | What it measures | Sample it needs | Main limitation | Where it fits |
|---|---|---|---|---|
| Visual inspection | Colour, markings, magnetism | The piece as it is | Cannot give a gold percentage | Deciding what to send |
| Acid / electronic jewellery testers | Comparison against jewellery karat references | A scratch or a clean surface | Dental alloys with platinum-group metals fall outside those references | Rough indication only |
| XRF on an unmelted piece | Elements in a thin surface layer of that piece | A clean metal surface | Describes one spot; plating, porcelain and mixed lots mislead it | Screening |
| XRF on the melted lot | Elements and proportions in the homogeneous melt | Melted, uniform metal; several spots read | Melting is irreversible | The measurement behind an offer (Dental Gold Experts' method) |
| Laboratory assay | Gold (and, with other methods, other elements) in a prepared portion | A homogeneous, weighed portion | Destructive, slow, laboratory only; standards written for bullion and jewellery | Refinery and laboratory settlement |
No method gives a meaningful result on a sample that does not represent the lot. The question to ask any buyer is not which instrument they own but "what do you test, and does it represent everything I sent?"
Which Metals Turn Up in Dental Restorations
A dental gold assay reports more than gold. The ADA resource lists gold, platinum, palladium, silver and copper as common constituents of noble alloys, and nickel, cobalt and chromium, with additions such as aluminium and molybdenum, in base alloys. In practice a mixed lot shows most of them:
- Gold (Au): the element most dental gold valuations centre on; present at anything from a trace to the greater part of a high-noble casting.
- Palladium (Pd): a major constituent of many "white" noble alloys, including copings under porcelain. A lot can be rich in palladium and low in gold.
- Platinum (Pt): a constituent of some high-noble alloys, usually in smaller amounts.
- Silver (Ag) and copper (Cu): common alloying metals in both noble and base formulations.
- Nickel, cobalt, chromium: the base-metal alloys, which by classification contain little or no gold.
- Porcelain, cement, tooth structure: not metals at all. They add to the gross weight and contribute nothing to the assay percentage.
The other metals a dental gold assay identifies describe the alloy and explain its colour and behaviour. The evaluation considers the composition of the dental alloy, its verified precious metal content and the applicable valuation terms; a lot that is mostly palladium-based white metal will show a low gold percentage, and the written report sets out the figures used.
How an Assay Result Becomes a Melt Value
"Melt value" is the market value of the gold contained in the metal. It has three inputs, all of which appear in a complete written report: the metal weight, the gold percentage from the dental gold assay, and a gold price. Here is the arithmetic with every figure assumed.
- Assume a lot of crowns and bridge units weighs 12 grams as received, and 9 grams after sorting and melting. The 9 grams is the metal weight.
- Assume the melted lot tests at 55% gold. Gold content: 9 g × 0.55 = 4.95 g.
- Convert to troy ounces: 4.95 g ÷ 31.1035 = 0.159 troy oz.
- Assume a gold price of $4,000 per troy ounce, a round figure chosen for the arithmetic; it is not today's price and not a price Dental Gold Experts uses. Value of the contained gold: 0.159 × $4,000 ≈ $637. That is the melt value.
- The offer is the melt value multiplied by the payout rate shown in the written report, so the offer is lower than the melt value.
Every figure above is assumed for illustration. Note what the example shows: the 3 grams of porcelain and cement contributed nothing, and a lot that "weighs 12 grams" contained under 5 grams of gold. Gold spot prices change daily; you can compare published prices from sources such as Kitco, the LBMA or the World Gold Council. Your actual offer uses the post-melt weight, the gold percentage measured by XRF, and the gold spot price shown in your written report.
The same arithmetic explains why two lots of equal weight can be worth very different amounts. At that same assumed price, 9 grams of melted metal at 40% gold contains 3.6 g of gold (≈ $463 of gold value) while 9 grams at 70% contains 6.3 g (≈ $810). Purity and weight have to be read together, and neither can be read from the outside of a crown; a dental gold assay supplies the purity figure.
To run the numbers for your own estimated weight and purity, use the dental gold value calculator; for what typical crowns contain, see how much gold is in a dental crown, and for the purity question in karat terms, what karat is dental gold.
Get a Measured Result, in Writing
Request your free prepaid, insured USPS shipping label. Your material is melted as one lot, the melted material is analyzed by XRF at multiple spots, and your written report shows the weight, gold percentage, gold spot price used, payout rate and payout calculation.
Weight, Purity and Payout: Reading the Numbers Correctly
Most disappointment in selling dental gold comes from mixing up quantities that sound alike. Three distinctions are worth fixing in mind before you compare offers; the worked example above shows all three at once.
- Received weight is not metal weight. A buyer who quotes "per gram" against the received weight and a buyer who quotes against post-melt metal weight are not quoting the same thing.
- Melt value is not the offer. The offer is the melt value multiplied by a payout rate, and every buyer applies one. A transparent buyer shows the rate; Dental Gold Experts shows it in the written report, and the offer is always below the melt value.
- A gold price is a moving number. What matters is that the price used is written in your report, so the offer can be checked against it and compared with a published price.
For dental practices and labs: a dental gold assay is the same whether the lot is one crown or a year of accumulated scrap. The steps do not change; the volume does. Lab sweeps, grinding dust and polishing waste are accepted on the same gold-content basis. Our guide for dental practices selling scrap and the dental office scrap gold SOP cover lot handling and record keeping, and sell dental gold is the starting point for any seller.
Questions to Ask Any Dental Gold Buyer About Their Assay
Understanding the dental gold assay process is most useful when it turns into questions. These are neutral; put them to anyone you are considering, including us.
- How do you determine the gold content? By appearance, by a reading on one piece, or by melting the lot and testing the melt? The answer tells you whether the figure will represent everything you sent.
- Which weight is the offer based on? Received weight, prepared weight or post-melt metal weight? Ask how non-metal material is handled.
- What is in the written report? Weight, gold percentage, the gold price used, the payout rate and the calculation are the minimum needed to follow the arithmetic. A single dollar figure is an offer, not a report.
- Which metals is the offer based on? Buyers differ. Ask which metals are measured, how each is measured, and what the offer takes into account. At Dental Gold Experts the evaluation considers the composition of the dental alloy, its verified precious metal content and the applicable valuation terms, and the written report shows the figures used.
- What happens before melting? Melting is irreversible. Ask whether you sign anything first and what it says.
- What are the terms if I decline? Ask what form the material is in afterwards and who bears which costs, and get the answer in writing before you ship.
- What are the shipping arrangements? Who pays, whether the shipment is insured, and what packaging is required. Dental Gold Experts emails a prepaid, insured USPS shipping label with packing instructions; the instructions use a USPS Small Flat Rate Box.
Our comparison of buyer types, best place to sell dental gold, applies these questions to pawn shops, jewellers, general gold buyers and specialists.
Next Steps With Dental Gold Experts
Get your free USPS shipping label
Request your label and we email a free prepaid, insured USPS shipping label and packing instructions, usually the same business day. Use a USPS Small Flat Rate Box, securely tape the outside edges, attach the label, and drop the box at any USPS location. For larger shipments, contact us before shipping to arrange additional coverage.
Melt, XRF, and written report
Blake melts your material as one lot and analyzes multiple spots on the melted material by XRF. Your written report shows the weight, gold percentage, the gold spot price used, the payout rate, and the payout calculation.
Accept and get paid
If you accept, we issue payment within 24 hours, usually immediately, by Zelle, PayPal, check, or ACH bank transfer. Receipt depends on the payment method.
The prepaid USPS shipping label and the assay are free · No minimum quantity
Get Your Shipping Label →Dental Gold Experts is based in Houston, Texas, and buys from individuals, dental practices and dental labs anywhere in the United States by mail; pickup is available in Houston, San Antonio, and Central Texas. Material is usually processed the day your package arrives or the next day. The full route from label to payment is set out in how to sell dental gold.
Have Your Dental Gold Measured, Not Guessed
Request your free prepaid, insured USPS shipping label. Everything you submit is melted together as one lot, Blake analyzes multiple spots on the melted material by XRF to determine its gold content, and your written report shows the weight, the gold percentage, the gold spot price used, the payout rate and the payout calculation. Payment is issued within 24 hours after you accept.
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