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What is an Assay?

When collecting or selling bullion or coins, you may have noticed that some items come in an assay card, or are accompanied by a certificate of authenticity. In the bullion industry, the definition of assaying has two meanings. In precious metal refining, an assay process is a test procedure for measuring and analyzing the purity of a metal. This procedure includes determining its composition in ores, alloys, mineral deposits and precious metals. This way mints assure that the bullion meets its precious metal standards of content and purity.

Gold smelting, refining.

Methods of Assaying

Assaying processes depends on the precious metal type and the particular piece that is being analyzed. Each assay starts with taking a rock or molten metal sample and continues with one of the following methods:

Destructive methods:

  • Fire Assaying – the oldest, most accurate, and destructive assay method. The sample is placed in a crucible and heated to find out the amounts of non-precious and precious metals. It’s a standard method for testing precious metal bullion in mints and refineries.
  • Dry Assaying – heating fluxes, special chemical cleaning agents, together with the sample, to let the precious metals separate, cool down and settle at the bottom.
  • Wet Assaying – dissolving the sample by using solvents and chemically analyzing the solution.

Non-Destructive methods:

  • Spectrograph Assaying – analyzing the intensity and strength of the light emitted by the sample when passing an electrical discharge through it.
  • X-Ray Fluorescence Assaying – identifying the precious metal and its purity by irradiating the sample with an X-ray beam. Analyzing the level of intensity of the X-rays emitted by the sample.

Other Assaying Methodssilver assaying through titration, gold assay by cupellation. Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) for assaying platinum.

Assay Types

Bullion pieces mostly arrive in assays as a special proof. Small bullion pieces are often sealed in assay cards which bear their date of creation and assay info. Larger bullion pieces usually come with an assay certificate which has a similar design and acts as a proof of authenticity and purity. Both assay cards and assay certificates assure the sellers and buyers that the bullion product is pure and legit.Gold bars is assay.

What is a Certificate of Authenticity?

A COA (Certificate of Authenticity) is a sticker or a seal placed on a piece of paper or certificate. This Certificate of Authenticity seal is a warranty that the bullion coin or piece is authentic. Though, unlike an assay, a COA doesn’t guarantee a thorough process which certifies the exact purity of the piece. The COA also doesn’t seal the bullion like the assay card does.

However, the COA displays essential details, such as the approval and authenticity stamp, the mint mark, and purity, serving as a proof that the bullion item is genuine. Some precious metal pieces don’t come with COAs, like bullion offered in bulk, or they may come accompanied with an assay instead.

Certificate of Authenticity

Assay products vs. COA products

Bullion bars ordinarily arrive with an assay proof because they are large, valuable, and have high purity. Limited or special coin releases, on the other hand, with a certificate of authenticity which proves their genuineness. Sometimes, limited edition coins and special bar releases also come with an assay.  

Precious metal assaying is fundamental both for producing and selling bullion. Both assays and certificates of authenticity assure the buyer or owner that the precious metal item was minted according to the mint’s standards and requirements of precious metal purity and content.

What Is The Difference Between Silver And Sterling Silver?

from the ore to your hand

What is the difference between silver and sterling silver? Have you ever seen these numbers – 900, 925, 999 or 9999 – on your jewelry piece or bullion item? Some of you probably still wonder what they show or stand for. 

Silver is a precious metal which you won’t find in nature in a 100% pure form. This means that we need to extract it from various ores or mix it with galena and argentite. To offer silver the well-known shape, the ores undergo several refining processes. These processes separate the silver from all other types of particles. Namely, the complexity of these refining actions is the key factor that defines the fineness (and value) of silver. Thus, the first four numbers, the silver grades, showcase the amount of fine silver in a specific precious metal piece. For instance, 900 means 90% pure silver, while the remaining 10% indicate that it consists of other metals.

The maximum purity can reach up to 99.99% or .9999 fineness. But the most popular highest silver purity is 99.9%, .999 or 999 – all three being the same, differing only by scale/notation. Silver with .999 fineness is called fine silver, actual silver, or pure silver; 99.99% pure silver – ultra-fine silver. Therefore, the silver having less than .999 fineness is sterling silver, being usually 92.5% pure.

Silver and sterling silver


What is Sterling Silver?

Silver in its original state is fully liquid. A 999 fine silver is not “suitable” for jewelry. Even the easiest attempt at making a ring from it makes the silver lose its shape. Thus, when we use silver in manufacturing jewelry items, we need to alloy it with other metals, such as nickel, copper, or zinc. These alloys make silver less soft and more durable. What is 925 sterling silver? In the US, pieces containing .925 silver and .075 copper, zinc or nickel are considered as sterling silver jewelry. In other countries, like Russia, the limit may be lower (.900 fine silver) and is regarded as enough for marking it as a silver product.

What is Fine Silver?

Solely 99.9% pure silver is admitted to be traded at trade markets, which means that this type of silver is used mostly for investment purposes. The .999 pure silver bullion bars, coins or rounds have been famous investment options for many years. Moreover, over the last decades, they appear as more optimal than pure gold items due to the silver’s limited resources, lower price, and increasing demand.

Silver bars are more common bullion pieces, which have standard sizes and almost no premium added to their production price. On the other hand, .999 silver coins are more valuable because of their collectability. Silver coins carry higher premiums since the minting process is more complex and they usually come in limited quantities. Each of these silver pieces is a signature product of a renowned mint: for example, the US Mint strikes the iconic American Silver Eagle, the Royal Canadian Mint the famous ultra-fine .9999 Silver Maple Leaf, the London Royal Mint – the beautiful Silver Britannia.

To trust or not to trust?

If you are wondering how to find the real purity of your piece despite its .925 or .999 mark, there are certain tips that will help you find out its actual fineness. Items carrying a 925 silver value will change in color over time since the nickel, zinc, or copper will interact with the oxygen or other elements in the air. You can test the 925 sterling silver by using a special acid kit. If you apply the acid to the silver item, it will change its color if the pieces have a fineness less than .925. However, we advise you to get your piece appraised by professionals in order to avoid any damages.

Do you own a pure or sterling silver item that you want to sell or authenticate?

Contact NYCBullion, and we will evaluate your pure silver or sterling silver piece with high accuracy. You can confidently sell any type of silver, including silver bars and scrap silver, as we guarantee the best services and quote on the market.

NGC & PCGS Graded Coins | How To Sell Graded Coins

What are graded coins?

Do you know how certain coins acquire their market value and what is the specific factor that certifies their authenticity? Graded coins are highly appealing to both collectors and investors because their grading serves (such as NGC or PCGS) as a guarantee of their value and authenticity. The grading process determines the physical condition of the coin – the so-called “state of preservation”. Coin grading became a usual practice in the United States beginning in the mid 19th century when the US Mint issued the first collectible coins.  

Top Coin Grading Companies

The coin’s grade is the key factor which determines the value of the coin. This grade is a sum of aspects, sometimes subjective ones, which place the coin in a certain category. This authentication process is performed solely by specific authorities who have strong knowledge in appraising gold coins and silver coins – the coin grading companiesIn the US, there are three main tiers for the coin grading companies based on their reputation and reliability. All grading companies, except NGC, PCGS, and ANACS, are in the lowest tier of grading services because of their reputation that is built on inconsistencies in rating coins.

For this reason, these companies charge a lower premium than the three exceptions mentioned above. America’s Oldest Coin Authentication and Grading Service (ANACS) is the middle-tiered grading company, the oldest on the market (as the title says), with grading regarded as acceptable. The top-notch grading businesses with the highest and most trusted rates are the Numismatic Guaranty Corporation (NGC) and Professional Coin Grading Service (PCGS). But what’s the difference between NGC and PCGS?! 


Both NGC and PCGS have an impeccable reputation, which makes the coins graded by them highly valuable on the market. These companies use the Sheldon scale, according to which, the coins get a grade from “1” to “70”. Both companies adopted this coin grading scale since their establishment (1986 and 1987 accordingly). NGC and PCGS also offer free access to their online databases of certified coins and an online coin grading guide for self-assessing the coin’s grades. The condition, value and the urgency for processing the request determine the coins’ premiums.

Over the last decades, NGC and PCGS became worldwide leaders in grading coins, especially the Chinese bullion coins. However, in spite of their similarities, there are still differences between these two coin grading services. NGC is keener in sharing detailed information about their grading process. They show that each coin is separately authenticated and graded by two experts, and, in case these two won’t agree on the coin’s grade, a third coin expert steps in. Besides, NGC is the coin grading service of the Professional Numismatics Guild and the American Numismatic Association. However, feel confident that any of the two top grading companies is definitely worth your choice.

PCGS graded coins  NGC graded coins

Grading coins – is it worth it?

NGC coins or PCGS coins? Certainly Yes!

Why? Because NGC and PCGS designations certify and assure a higher numismatic value to your bullion coin. Graded coins become a guaranteed product and acquire the reputation of the grading company.

Are “First Strike” coins really the very 1st coins?

The US Mint, just like most mints, do not issue first strike coins. It’s very hard to keep track of the exact order of manufactured coins during their striking. The “First Strike” designation (PCGS) certifies that the coins arrived for grading within the first 30 days of issue from the mint. NGC also used to apply the “First Strike” label, but it changed to “Early Releases”. Are first strike coins worth more? This designation is highly regarded among enthusiastic collectors. The label obviously adds a higher premium to coin’s initial market price. However, there is no proof that the “First Strike” or “Early Releases” coins will keep their value in time. 



Do you own a graded coin which you would like to sell or authenticate? Contact NYCBullion, and we will appraise with high accuracy any of the following coins, graded and nongraded:

How To Test If Gold Is Real

A true symbol of high status, success, and prosperity, gold is a luxurious, highly desired precious metal. However, even if you own a stamped gold piece, its hallmark isn’t a guarantee of its real gold content. This article reveals you the best testing methods on how to perform a proper gold test. Remember that you can always get a free top-notch appraisal from our expert NYC Bullion team.

Gold Properties

Before proceeding to any testing, you should know that gold is considered a long-lasting metal since it:

  • Doesn’t tarnish or rust
  • Is non-magnetic
  • Conducts heat and electricity
  • Is dissolved only by nitro-hydrochloric acid (1:3)
  • Is malleable, ductile, and sectile – easy to hammer, press and cut into different shapes

Since gold is sectile, it also needs to be alloyed with other metals. Its alloys are measured using either the Karat system or the Millesimal Fineness System. One Karat unit is equal to a 1/24 part of pure gold in an alloy while the millesimal purity is indicated by parts per thousand of genuine gold by mass in an alloy. Take a look at the below gold purity chart for more details.


Karat System % of Gold Content Millesimal Fineness System Gold or not gold

(US standards)

8K 33.3 333 Not gold
9K 37.5 375 Not gold
10K 41.7 417 Gold alloy
14K 58.3 583 (585) Gold alloy
15K 62.5 625 Gold alloy
18K 75.0 750 Gold alloy
20K 83.3 833 Gold alloy
21K 87.5 875 Gold alloy
22K 91.6 916 Gold alloy
23K 95.8 958 Gold alloy
24K 99.9 999 Pure Gold

To find out whether your gold jewelry or bullion piece is fake or genuine, use the following gold testing methods. Home methods will help you easily test for real gold while professional tests will reveal the exact fineness of your piece.

The Magnifying Glass Test

the magnifying glass test

The first and simplest home test for gold requires just a magnifying glass and your gold bullion or jewelry. Carefully inspect your piece with the magnifying glass for these visual clues:

  • any signs of discoloration – gold doesn’t react to any environmental factors. So, if your piece has discoloration marks, it’s either not gold or gold plated.
  • color and shininess – pure gold is not very shiny and has a nice soft yellow color. Any shiny, yellow or toned(reddish) item is definitely not pure gold.

Hallmark/Stamp/Jewelry Markings Test

hall mark.stamp test

The second step is the hallmark test, for which you may also need a magnifying glass. Look for any gold hallmarks or jewelry hallmarks (inside the surface or near the clasp). These markings must show at least the gold’s purity (in millesimal fineness or Karats) and, if selling jewelry, it can also be accompanied by the manufacturer’s stamp.

Beware of “HGP,” “GF,” “HEG,” “GP,” “HGE,” “RGP,” “GEP,” or ”GP” hallmarks because they all mean that the item is gold plated. Also, avoid fake “800,” “925” or “950” marks on gold pieces since these are all silver hallmarks. The hallmark test isn’t 100% accurate and shall be used only to identify if the gold is not genuine or pure. If your item is marked as gold, but you’re still in doubt, proceed with further testing.

The Skin Test

skin test

The skin discoloration test is one of the easiest ways to test gold at home. Just hold your gold piece in your hand for a few minutes. Real gold doesn’t leave any spots or stains on skin, so if you notice a black or green chemical reaction with your perspiration, then it’s certainly an alloy.

However, keep in mind that if you apply powder or liquid foundation on your tested skin area, a real gold item might leave a black streak on it, so your testing won’t be precise. Therefore, before performing the gold test, please ensure that you aren’t wearing any makeup and your skin is clean.

The Float Test

The Float Test

Another easy method of testing gold jewelry or bullion at home is the float test, for which you need to place your gold piece in a cup of water. Due to gold’s high density (19.32 g/ml), pure gold will immediately sink to the cup’s bottom. Fake or plated gold will hover or float above, while gold alloys will tilt up halfway. Also, if your piece will rust or discolor, then it’s fake.

However, please consider that a fake item could consist of other heavy metals which also sink. So, use this test to spot fake gold that floats or hovers. If your item sank and you still have doubts, take another test.

Porcelain Tile Test (or the Scratch Test)

Porcelain Tile Test (or the Scratch Test)

The porcelain tile test, also known as the gold scratch test, requires a ceramic plate or a piece of unglazed porcelain tile. Scratch or rub your gold across the tile/plate and take a look at the color of the streak. A golden, yellow streak indicates real gold while a black streak shows that your item is fake or it’s pyrite. If you don’t want to damage your gold piece, consider using other harmless testing methods.

The Magnet Test

The Magnet Test

One of the easiest and most convenient home gold tests is the magnet gold test for which you need a high strength magnet. This solution is cheap and portable since a magnet is accessible anywhere and anytime. Because genuine gold is not magnetic, it won’t be attracted by the magnet. Gold allows or fake items will instantly attract the magnet while slightly attracted pieces are more likely gold plated. Also, keep in mind that jewelry pieces usually have strength elements (like wires, clasps) which aren’t made from gold and can be magnetic.

Thus, if the magnet attracted your item, you can skip the following tests. Otherwise, it’s likely pure gold, and it may need further testing for a higher accuracy. Also, remember that other precious metals (like silver) are also non-magnetic, so make sure to perform additional testing to certify that your item is real gold.

The Acid Test

The Acid Test

If you don’t mind damaging or scratching the samples, you can apply the gold acid test. You need to purchase a gold testing acid kit (for each Karat), a black gold testing stone, gold Karat needles and 2 glass beakers. One beaker with baking soda/water mix and other just with water. Before testing gold with acid, be sure to choose a well-ventilated area and to take all the safety measures for protecting yourself and your working area from any contact with the acid.

Each bottle from the acid kit is a distinct mixture of nitric acid and other components. Take your gold sample and scratch a slight line on the black stone, making sure you’ve reached over any potential plating. Mark your line and make similar parallel lines with the other gold Karat needles. Then take the lowest karat acid and apply its content across or on each line and wait for 30 seconds. Wash the stone in the baking soda/water mixture then rinse it in water and pat it with a paper towel.

A reaction (dissolved line) shows that your sample has a lower purity, a slight reaction means that you’ve matched the Karat while no reaction indicates that you have a higher Karat gold. If your sample didn’t react, repeat the test steps with the next acids until you match the Karat. If the last test acid in the kit is for 22K and you need to know whether your piece is 23K or 24K, you should use gold testing machines.

Gold Testing Machines – Electronic and XRF Thermo Gold Test

Electronic and XRF Thermo Gold Testers

The most harmless and accurate testing methods are the XRF thermo and electronic gold testing machines, such as the Sigma Metalytics Precious Metal Verifier and XRF Thermo Scientific Analyzer.

Sigma metalytics machine

This device performs gold test for bullion and jewelry without using chemicals or damaging them. It uses electromagnetic waves to determine the Karat of your item based on gold’s electrical characteristics. The waves penetrate deeply into the tested piece, ignoring its surface and assessing its body, then displaying the result in a few seconds.

The Sigma Metalytics electronic gold tester comes with various sized sensors for each gold sample. Moreover, if you want to sell gold coins or any other gold bullion that is encased, you don’t have to remove them from their protective holders. Just place your sample on the corresponding sensor, select the expected purity, wait for the “Ready” message and press “RUN/CAL.” If the result is between the brackets, your tested piece matches the selected fineness while an up arrow indicates that your piece is not gold.

XRF Thermo Scientific™ Gold Test

It’s the most expensive precious metal tester, yet the most accurate and nondestructive one. This gold analyzer uses X-ray fluorescence (XRF) spectrometers to test the gold piece. The device sends X-rays through the sample and makes atoms get momentarily excited, moving them into a higher energy state. When the atoms return to their ground state, they release radiation which is detected and read by the machine. The machine returns the exact Karat or metal composition of the tested piece. It also comes with a unique AuDIT™ gold-plating detection technology which alerts you if the tested item is gold plated.

Free 100% Reliable Test – Free Professional Appraisal

The best and easiest testing method when selling gold is to get analysis and evaluation by professional appraisers, like NYCBullion. Our team uses high-class digital gold testers, including the Sigma Metalytics Precious Metal Verifier and XRF Thermo Scientific Analyzer. Along with our top-notch expertise, we guarantee a free, fully transparent appraisal of your goods and the most generous quote on the market. You can get your free evaluation from NYCBullion either by sending your gold item or by visiting our store. For any questions, just call us at (212)-354-5557, message us, or, come to our retail office at 32 West 47th Street, Booth 41, New York, NY 10036.