What metals cannot be detected by a metal detector? If you are familiar with this device, you know it can locate almost every metal buried underground. For this reason, you may wonder whether or not there are metals that it cannot detect.
A metal detector cannot find metals with low electrical conductivity. The device works by transmitting and receiving electromagnetic fields. Hence, metals need to be good conductors for it to detect them. The most challenging metal for a metal detector to detect is stainless steel.
What Metals Cannot Be Detected by a Metal Detector?
Metal detectors work excellently for finding valuable objects like coins and jewelry. Since such a device can detect ferrous and non-ferrous metals, it can be pretty easy to pinpoint where your targets are buried.
So, this hobby can be worth the effort and time investment because you can find valuables that you can exchange for money.
However, what metals cannot be detected by a metal detector?
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Are There Metals That Metal Detectors Cannot Find?
Metal detectors emit electromagnetic fields to locate metals buried underground. These electromagnetic fields change from time to time as the device listens to waves that come from conductive elements.
That said, a metal detector will not detect metals with poor electrical conductivity.
Below are metals that a metal detector cannot detect:
1. Stainless Steel
Stainless steel is an alloy of iron and chromium. The chromium content produces a thin film of chromium oxide on the surface of the steel. This layer is known as the passivation layer.
The passivation layer prevents the stainless steel from corroding. Additionally, this metal sometimes has other elements, such as silicon, carbon, and manganese.
Moreover, stainless steel is a non-ferrous metal, so it is one of the metals that a metal detector cannot detect. The reason is that it has low electrical conductivity.
Additionally, stainless steel has a low magnetic permeability. Meaning it cannot produce enough signal for a metal detector to recognize. (source)
Titanium is a useful, strong, corrosion-resistant, and lightweight alloy. People utilize it in many products like dental implants and jewelry.
Like stainless steel, an ordinary metal detector cannot locate titanium as it has low electrical conductivity. (source)
However, a particular type of metal detector can locate aluminum – the Very Low Frequency (VLF) metal detector. Such a device transmits single-frequency sine waves that are usually at high-pitched frequencies. This way, a VLF metal detector can locate low conductors. Still, you need to optimize the device to a particular setting to find titanium.
3. Ceramic Ferrite Magnets
Ordinary magnets contain either iron or iron combined with copper, cobalt, or neodymium. These metals are highly conductive, making it easy for metal detectors to locate them.
However, ceramic ferrite magnets are ceramic compounds mixed with iron oxide, strontium, nickel, and zinc.
There are only low amounts of the said metals found in ceramic ferrite magnets. For this reason, this type of magnet almost has no conductivity. As a result, metal detectors will not be able to detect it. (source)
How Metal Detectors Work
Metal detectors are high-end devices. They do not work on magnetism but rather by detecting electromagnetic fields. For this reason, the device can detect both ferrous and non-ferrous metals.
Ferrous metals consist of iron. Such a type of metal is corrosive and magnetic. They are known for their durability, hardness, and strength. Some examples of ferrous metals are alloy steel and cast iron, both detectable by a metal detector.
On the other hand, non-ferrous metals, such as copper and aluminum do not contain iron. For this reason, non-ferrous metals are non-magnetic. Some non-ferrous items are coins and jewelry, which a metal detector can also detect.
That said, metal detectors can locate almost all types of metals. The reason is that the device works by transferring an electromagnetic field from the search coil into the ground. However, it is essential to note that there are metals that a metal detector cannot detect.
Once the electromagnetic field hits a metal target, it will retransmit an electromagnetic field into the device’s receiver coil. Any metal target will send a signal regardless of whether it is ferrous or non-ferrous.
For this reason, there are only a few metals that a metal detector cannot detect. These metals have low electrical conductivity, making it impossible to create an electromagnetic field. (source)
Does a Metal Detector Detect All Metals?
A metal detector is a device that consists of a search coil and a receiver coil that transmits and receives electromagnetic fields, respectively. It also has a loudspeaker for alerting the operator in the presence of metals.
As mentioned, metal detectors locate metals underground using an electromagnetic field. This factor makes both ferrous and non-ferrous metals detectable. That said, these devices can detect all metals as long as they are electrically conductive.
In addition, a metal detector can find ferrous meals better due to their magnetic properties. On the other hand, non-ferrous metals are detectable due to their electrical conductivity. (source)
For instance, both general-purpose and high-end metal detectors can locate
A metal detector’s ability to detect all types of metal can be troublesome if you are looking only for a particular kind of metal. The reason is that there are a lot of metal pieces, such as aluminum foils, tin cans, iron nails, and screws, buried in the ground. These metals can interfere with what you are looking for, thus making the search more difficult.
Fortunately, metal detectors can ignore metals and focus only on the target you are seeking.
Metal Detector Discrimination
Inevitably, some metals are undetectable by a metal detector. On the contrary, you can also set a metal detector to detect only a particular type of metal. It is possible as most metal detectors have a discrimination feature.
Discrimination is the device’s ability to ignore certain metals buried underground. Instead, it will only alert the operator once it locates a target that it identifies based on ferrous properties and conductivity.
To simply put it, setting your metal detector discrimination is like telling your device to be quiet when it senses invaluable targets.
Moreover, the discrimination feature varies in metal detectors:
A dial sets variable discrimination. This dial increases and decreases how much discrimination your metal detector is set to respond to.
In addition, variable discrimination is helpful if you are used to operating a metal detector. The reason is that such people already know how much or how little discrimination they need to apply when finding targets.
Metal Detecting Tip: Heck I could probably write a book on setting the discrimination on a Metal Detector. When you learn how to do it correctly treasure seems to jump out of the ground. Read – How to Set the Discrimination on a Metal Detector
This type of discrimination prompts the metal detector to identify a notch or notches in the uninterrupted conductivity range. This way, the metals within the notched-out area will either be included or excluded in the target finds.
Additionally, metal detectors feature proprietary discrimination settings. This feature allows the devices to improve their notched discrimination setting further. You can run the metal detector to notch reject or notch accept targets.
Notch reject prompts the metal detector to ignore every metal within the notch range. On the other hand, the notch accept mode lets the device receive everything in the notched range.
Moreover, it is essential to note that not all metal detectors have discrimination settings.
Pulse Induction (PI) metal detectors use a different technology when locating targets. For this reason, they usually do not feature a discrimination mode. (source)
Do Diamonds Set Off a Metal Detector?
Metal detectors are good for finding silver, gold, and jewelry. So, the question of whether or not it can locate diamonds seems to make sense.
But as mentioned, metal detectors can only locate ferrous and non-ferrous metals. So, it will not detect diamonds as they do not have metallic properties. The same principle applies to gemstones and pearls.
However, you can detect a diamond embedded in a ring. This piece of jewelry usually consists of silver, gold, or other malleable metals that are electrically conductive.
Furthermore, your metal detector will not detect other items such as papers, bones, gemstones, stone figures, and pearls. (source)
Will Silver Set Off a Metal Detectors?
Silver is one of the most common metals used for making jewelry. For this reason, it is understandable if metal detector users are trying to target silver jewelry when they are metal detecting. But will this metal set off a metal detector?
There are nine major types of silver. To see if they will set off a metal detector, let us look at the composition of each of them.
|Fine silver (.999 silver)||Fine silver is the closest grade to the pure element silver. It is sometimes called .999 silver, which indicates that it is 99.9 percent pure. The remaining 0.1 percent consists of trace elements that are insignificant in quantity.|
|Sterling .925 Silver||This type of silver is the standard quality for jewelry in the United States and most global markets. It consists of 92.5 percent silver, while the remaining 7.5 percent is copper. Sometimes, sterling silver also comes as an alloy of silver and nickel to increase its hardness.|
|Argentium Silver and Non-Tarnish Alloys||Non-tarnish alloys are relatively new to the market. Argentium is a brand of silver, but there are similar alloys available. The alloys are usually 92.5 percent silver, but some have higher silver content. The remaining metals consist of copper and the element germanium.|
|Coin Silver||Coin silver was a standard alloy in the United States back then. However, it is relatively rare now, so finding it with a metal detector is like finding a great deal. This type of silver alloy is 90 percent silver and 10 percent copper. Moreover, many coin silver pieces are considered antiques.|
|Silver-Filled||Silver-filled metals are not alloy. The reason is that their metal content varies throughout the material. Silver-filled has 5 or 10 percent sterling silver on the external layer. Manufacturers then use heat pressure to fuse the silver layer to a brass core.|
|Silver Plated||Silver-plated is a base metal type of silver. It has a very thin layer of silver on the surface, with alloy as a base metal. That said, this type of silver only has a tiny fraction of silver in it.|
|Nickel Silver||Unlike the other types of silver, nickel silver does not actually have the element silver in it. Instead, the term “silver” only describes the color of the metal rather than its content. Nickel silver is a base metal alloy that consists primarily of copper combined with either nickel, zinc, or a combination of the two.|
|Tibetan or Tribal Silver||Just like nickel silver, tribal silver is base metal alloys. They do not have any silver content but are silver in appearance, making them an inexpensive alternative to authentic silver jewelry. Moreover, the alloy content of Tibetan silver varies immensely. Some imports from exotic lands even have dangerous metals, such as lead.|
|Thai, Bali, or Mexican Silver||This type of silver has sterling silver and nickel as a filler metal. (source)|
Silver jewelry all contain alloy metals. The most common metals added to them are copper and nickel. Moreover, these metals are good conductors of electricity. For this reason, silver is not one of the metals that a metal detector cannot detect.
In addition, silver is the best element to conduct electricity. So, if there is a silver piece of jewelry in the area where you are metal detecting, it will undoubtedly set off a metal detector. Even silver-plated metals can set off a metal detector. (source)
Will Graphite Set Off a Metal Detector? (Hot Rocks)
Graphite is a naturally occurring element that comes in crystalline carbon, which you will commonly find in igneous and metamorphic rock. That said, graphite is a form of the mineral.
Additionally, this mineral is exceptionally soft, making it split even at a little bit of pressure. Graphite also has a very low specific gravity.
That said, graphite is non-metal. But despite this factor, it can still conduct electricity. For this reason, you might think that a metal detector can detect it since the device utilizes an electromagnetic field to find metals. But on the contrary, you may think that it is not a metal, and a metal detector cannot detect only a few metals.
However, graphite belongs to what is called hot rocks. For this reason, it will set off metal detectors despite being a non-metal element.
According to Sherman Troy in his book How to Use a Metal Detector for Treasure Hunting, “hot rocks refer to stones that have absorbed significant amounts of minerals such as zinc and iron.” He added that hot rocks can “cause false positive signals.”
Metal Detecting Tip: Learning more about “rock rocks” can improve your treasure finding odds. Read more about what hot rocks are and setting up your machine in this article: What Are Hot Rocks Metal Detecting
Graphite is a form of hot rock. Hot rocks, such as pebbles and elements, contain low conductive minerals. These rocks can disrupt metal detector signals by sending alerts when valuable metals are buried in a specific area.
Moreover, there are two types of hot rocks – negative and positive.
Negative Hot Rocks
Negative hot rocks contain high Magnetite concentrations – an Iron Oxide that turns rock and sediments into black. The iron oxide molecule also has a high atomic weight, making rocks and sediment heavy.
Moreover, one of the most common types of negative hot rocks is black sand. It has a high amount of Magnetite, allowing it to set off a metal detector.
But while your metal detector can read this response, the sound the device will produce is less definite than the sound coming from real targets.
A delayed acquisition often accompanies the false-metallic audio response. There is also a nulling audio response when you move the search coil away from a negative hot rock.
Positive Hot Rocks
Positive hot rocks are good conductors of electricity. They contain high Maghemite concentrations – an iron oxide that causes rock and sediment to become red, reddish-orange, and even yellow.
In addition, positive hot rocks are good conductors of electricity. They consist of high concentrations of sulfide minerals, specifically Pyrrhotite and Bornite.
Moreover, graphite is a form of positive hot rock. So, if your metal detector is set to a low level of sensitivity, it will be able to detect signals from graphite. As a result, the graphite can interfere with your metal detector’s signal. (source)
What We Learned
There is no denying that metal detectors are highly technological devices. For this reason, it can detect almost every type of metal that is buried under the ground. If you are lucky enough, you may even find valuable metals, such as gold, silver, and jewelry.
However, it is essential to note that there are metals that a metal detector cannot detect. The reason is that these metals have low electrical conductivity, so they cannot create an electromagnetic field for metal detectors to read.
In addition, metal detectors are not meant for finding non-metal elements, such as gold, gems, and pearls. But if these elements are on metal jewelry like rings and necklaces, you may detect a valuable find in the area where you are metal detecting.
Learning How to Use Your Metal Detector Can Be Tough, But I’ve Got You Covered with These Articles
- What is a Pulse Induction (PI)- What is a PI and how to properly use it
- Can you Metal Detect in the Winter – Yes but read this article to learn the tips and tricks.
- Metal Detecting Digging Tools Complete Guide – Digging is part of metal detecting get the tools to do it right.
David Humphries, Writer and Creator of METAL DETECTING TIPS. After borrowing my son’s detector and finding $.25. I felt like a treasure hunter. FREE MONEY! I was seriously bitten by the metal detecting bug.
- Daniel Y.C Fung and Richard F. Matthews, Instrumental Methods for Quality Assurance in Foods. Marcel Decker Inc., 1991. https://books.google.com.ph/books?id=uFMPEAAAQBAJ&pg=PA162&dq=can+stainless+steel+be+detected+by+a+metal+detector&hl=en&sa=X&ved=2ahUKEwjjopPFzPT0AhVGslYBHcmEBdIQ6AF6BAgHEAI#v=onepage&q=can%20stainless%20steel%20be%20detected%20by%20a%20metal%20detector&f=false.
- Beth Israel Lahey Health Winchester Hospital, “Evidence for the Health Claim.” True or False: Surgical Hardware in the Body Sets Off Airport Metal Detectors (blog). https://www.winchesterhospital.org/health-library/article?id=157005.
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- Brandon Neice, The Metal Detecting Bible: Helpful Tips, Expert Tricks and Insider Secrets For Finding Hidden Treasure. United States: Ulysses Press, 2016. https://books.google.com.ph/books?id=mvxkCwAAQBAJ&pg=PA10&dq=what+can+metal+detectors+detect&hl=en&sa=X&ved=2ahUKEwjIn7Cmz_T0AhWLdXAKHXcsBXAQ6AF6BAgFEAI#v=onepage&q=what%20can%20metal%20detectors%20detect&f=false.
- Robert M. Dunn and John H. Mutti, International Economics, USA: Routledge, 2004. https://books.google.com.ph/books?id=jPjsj3_8S3wC&pg=PA298&dq=Do+Diamonds+Set+Off+A+Metal+Detector?&hl=en&sa=X&ved=2ahUKEwihz5DOz_T0AhVXc3AKHZUPBhMQ6AF6BAgJEAI#v=onepage&q=Do%20Diamonds%20Set%20Off%20A%20Metal%20Detector%3F&f=false.
- Donald Clark, CSM IMG, “Silver.” Jewelry Metals 101: Gold, Silver, and Platinum (blog). https://www.gemsociety.org/article/jewelry-metals-overview/#Silver.
- Sherman Troy, How to Use a Metal Detector for Treasure Hunting: Metal Detecting Tips and Guide You Need To Read. Lulu Press Inc., 2014. https://books.google.com.ph/books?id=-UdaCAAAQBAJ&pg=PT33&dq=what+are+hot+rocks+in+metal+detecting&hl=en&sa=X&ved=2ahUKEwjItIed0_T0AhUZMd4KHRRGAOAQ6AF6BAgHEAI#v=onepage&q=what%20are%20hot%20rocks%20in%20metal%20detecting&f=false.