Buzz
Odor is not typically something that comes to mind when thinking about rocks. Most mineralogy textbooks don't mention the smell of rocks and minerals. While it's true that most rocks are odorless, there are some exceptions.
10. Antozonite
Antozonite is a type of fluorite mineral that ranges in color from dark violet to black. While it’s common for minerals to have nicknames, Antozonite has a few. In German, it’s referred to as “stink-fluss” and “stink-spat,” while in English, it’s called “stinkspar” and “fetid fluorite.” This rare fluorite variant is notorious for its foul odor.
When Antozonite is fractured or crushed, it gives off an overpowering stench. The odor comes from fluorine gas trapped in the tiny, porous spaces within the mineral. Once the pores are broken, the harsh fluorine gas escapes and reacts with oxygen and hydrogen in the air, producing a pungent mixture of ozone gas and hydrofluoric acid vapor. This foul-smelling combination is enough to repel any nearby noses. Fetid fluorite certainly lives up to its name.
9. Sphalerite
Sphalerite is often referred to as the ‘scratch-and-sniff’ mineral. Composed of iron, zinc, and sulfur, it is the primary source of zinc ore. Sphalerite can be found in mineral-rich regions known as sulfide deposits. Although it can form beautiful transparent crystals ranging from yellow-brown to black, it frequently appears as a dull, dark lump with shades of yellow, red, brown, or black. Many other minerals can resemble these unattractive lumps with varying color tints.
Due to the wide color variation of sphalerite, almost every student in mineralogy has been taught a simple scratch-and-sniff method to identify it. The test involves scratching the mineral against a piece of unglazed porcelain (a streak plate) and then smelling the scratched surface. The streak will appear yellow, and the mineral will emit a sulfur-like odor similar to a just-lit match.
8. Jet
Lignite is the lowest-quality grade of coal. True to its nature as a fossil fuel, many pieces of lignite contain actual fossils, often preserving the shape of trees and branches. In the 19th century, Victorians polished and carved lignite to a high shine, using it in jewelry and calling it jet. The seaside town of Whitby, located on England's northeastern coast, is the most famous source of jet.
Queen Victoria made Whitby and its jet famous. After the death of her husband, Prince Albert, Victoria wore mourning black for the rest of her life. She embraced Whitby jet jewelry because it was one of the few stones that complemented her all-black wardrobe, making jet the only fossil fuel that serves as a fashionable accessory.
A common method to identify jet is by using a heated needle. When you press the hot needle into the rock, jet will give off a scent reminiscent of burning tar or coal. In contrast, black plastic will emit the odor of burning plastic, and black gemstones like onyx or hematite won’t release any smell. The hot needle will leave a small pit in the surface of the jet, so it’s best not to try this method on antique Victorian jewelry, like your grandmother's brooch.
7. Pyrite
Many sulfide minerals are notorious for their sulfur-like stench. Pyrite, also known as 'fool's gold,' is the shiny, gold-colored mineral that is often mistaken for real gold. However, pyrite contains no gold, only iron and sulfur. Sadly for prospectors, pyrite and gold are often found together. There are a few ways to differentiate pyrite from gold, and one of them involves using your sense of smell.
When gold is heated, it remains odorless, but warming up pyrite causes it to emit a strong smell. The heated pyrite releases sulfur into the air, which reacts with oxygen and hydrogen, forming hydrogen sulfide and sulfur dioxide. Hydrogen sulfide (HS) produces the unmistakable scent of rotten eggs, while sulfur dioxide (SO2) gives off the smell of brimstone, the poetic term for burning sulfur. Hot fool’s gold: It stinks!
6. Arsenopyrite
Not all sulfide minerals smell like sulfur. There is one that shines like pyrite and contains sulfur and iron just like pyrite (along with one additional element), but when struck with a hammer or scratched with unglazed porcelain, it releases a garlic-like odor! Even if you love garlic, avoid inhaling this mineral's scent, as the extra element is arsenic. This mineral is arsenopyrite, a pale yellow lookalike of pyrite.
The garlic scent actually comes from arsenic trihydride, commonly known as arsine gas. While the small amount of toxic gas released from scratching or striking arsenopyrite is unlikely to harm an adult, it's not something you want anywhere near children or pets. It may be visually appealing, but arsenopyrite doesn't belong on the kitchen windowsill or in the dining room centerpiece.
5. Anthraconite
Anthraconite is a black limestone composed of calcite and bitumen, often called “stinkstone” or “swinestone.” Bitumen is a black, sticky substance used in making asphalt, although many North Americans refer to both the tar-like substance and the road surface as “asphalt,” while Australians commonly use the term “bitumen” for both. Regardless of terminology, anthraconite contains bitumen.
When you rub anthraconite with a cloth or heat it, it earns its nickname by emitting a foul, tar-like odor. Fortunately, it's a rare rock, found in only a few locations such as Michigan and Ontario in North America, and Saxony-Anhalt in Germany.
4. Amber
Amber is another organic gemstone with its own distinctive scent. Like Whitby jet, amber is a fossil, but in this case, it’s fossilized resin that dates back millions of years. Unlike jet, which is black and opaque, amber is a transparent stone that ranges from yellow to red, and it’s often found washed up on beaches along the Baltic Sea. Due to its lower density compared to saltwater, amber can float on the ocean's surface. Deposits are scattered across the globe, with notable finds in Alaska, Prussia, Latvia, New Jersey, Kansas, and the Dominican Republic.
To release the characteristic scent of amber, the hot needle test can be used: heat a needle and insert it into the amber. The resulting fragrance is similar to burning pine sap or woody incense, but with an extra smoky note. This test also leaves a small pit in the amber.
The pine-like aroma produced by heating amber is quite different from the “amber scent” or “amber essential oil” marketed in perfumes. The term “amber” in the fragrance world is not related to the actual gemstone. It’s based on modern wood oils and has nothing to do with the stone itself.
3. Kaolinite
Kaolinite, also known as China clay, is a fine white clay named after the Kao-Ling Mountain in China. It is widely used in the production of ceramics and, surprisingly, is safe to eat. While eating clay may seem unusual, kaolinite has been consumed for centuries and is found in medicines and even toothpastes.
Until the late 1980s, Kaopectate, a popular anti-diarrhea medication, contained two main ingredients: kaolinite and pectin. Pectin, a tasteless sugar compound, is a soluble fiber and thickening agent commonly used in jams and jellies, while kaolinite’s fluid-absorbing properties helped fight diarrhea. Anyone who remembers the original Kaopectate will recall its chalky, clay-like scent—a direct result of kaolinite.
2. Sulfur
No discussion about stinky rocks would be complete without mentioning brimstone, a rock made infamous by the Bible. The first well-known reference to brimstone appears in the Book of Genesis, Chapter 19, Verse 24: “Then the Lord rained upon Sodom and upon Gomorrah brimstone and fire from the Lord out of heaven.” Equally iconic is the lake of fire and brimstone mentioned in Chapter 21, verse 8 of the Book of Revelation: “The fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone.”
The word “brimstone” is an ancient term for sulfur, derived from the Old English word “brynstan,” meaning “burning rock.” Sulfur and fire are commonly found together in volcanic regions, where volcanic gases deposit sulfur on the surfaces of volcanoes and steam vents known as fumaroles. Due to sulfur’s flammability, volcanic eruptions often ignite sulfur deposits. In nature, fire and brimstone go hand in hand. Interestingly, pure sulfur is odorless, but it’s the sulfur dioxide released when sulfur burns that creates the characteristic smell of fire and brimstone.
1. Oil Shale
Shale, a clay-laden sedimentary rock, is found in many places across the globe. When it gets wet, it often emits a smell reminiscent of mud or damp earth. However, the rock type known as oil shale gives off an odor similar to diesel or tar. This distinctive smell comes from a petroleum-like substance called kerogen. Though kerogen has the appearance of oil, it isn’t quite there yet—it requires heating or treatment with solvents to transform into actual oil.
Extracting oil from oil shale is a challenging process. Shale naturally resists fluid flow, including water and oil, making it difficult to get the kerogen out and turn it into oil. Even if kerogen could be converted into oil within the shale, the process of pumping it out is costly and difficult, often leading to environmental damage, especially to groundwater. Though oil shale can be mined and treated above ground, this too is an expensive and environmentally taxing endeavor.
It will likely be many years before oil shale becomes a major source of oil. Nevertheless, it’s not hard to find exposed oil shale in regions where it’s abundant, such as Northwestern Colorado in North America or coastal Queensland in Australia. On a warm, windless day, simply follow the scent to find it.
