The rarest and most precious of all watch case materials is not gold or platinum like you might expect, but a metal you’ve possibly never heard of: tantalum. There’s a good reason for this. Tantalum is the rarest stable element in our entire solar system, with just one atom of tantalum for every 181 billion atoms of other elements. That makes tantalum far less abundant than gold, or any of the traditional precious metals. In addition to its scarcity, tantalum possesses noble qualities that elevate it from all other metals when it comes to watchmaking and jewellery. Perhaps foremost amongst these is tantalum’s incredible durability in its pure, unalloyed state.
Watch cases are typically made of alloys, or a mixture of different metals aimed at achieving three main criteria: hardness, strength and corrosion resistance. Pure gold is too soft to retain its shape, so it is alloyed with other metals to provide strength. A typical 18K solid gold dress watch is made up of 75% gold with 12.5% copper and 12.5% silver mixed in, and in this composition, it achieves a passable hardness of 135 Vickers and a tensile strength of about 500 MPa, which measures how many megapascals of force is required to break the material. Another common metal for watch cases is 316L steel, a complex alloy made up of 10 different elements. This modern stainless steel achieves a hardness around 155-200 Vickers and a tensile strength around 515 MPa, making it more hard-wearing than 18K gold.
Tantalum requires no such metallurgical shoring-up of weaknesses. In pure elemental form, it boasts a hardness of 200 Vickers and a tensile strength of 900 MPa, making it just as hard and almost twice as strong as the best steels. In addition to this, tantalum is practically immune to all forms of corrosion. Although we refer to 316L as “stainless” steel, this alloy can still suffer from pitting and crevice corrosion in chlorinated water and surface corrosion in saltwater. Tantalum laughs in the face of such weak corrosives, as harsh chemicals and strong acids have no effect on it whatsoever. Even Aqua Regia, the king of all acids (aka “Royal Water”, so named by alchemists for its ability to dissolve the noble metals like gold) cannot attack or harm tantalum.
This imperviousness to acids and corrosives is where tantalum got its name. It was first discovered in 1802 by Anders Gustav Ekeberg, a Swedish scientist and expert in Greek literature. Befitting his area of expertise, Ekeberg named the new element from the Greek myth of Tantalus, who was condemned to stand knee-deep in water which forever tantalised him by receding away whenever he attempted to drink. Ekeberg wrote: “This metal I call tantalum … partly in allusion to its incapacity, when immersed in acid, to absorb any and be saturated.” To paraphrase this rather archaic explanation: like mythological Tantalus, tantalum can be immersed for all eternity and never be quenched.
Usability in its pure state also lends tantalum another important attribute for jewellery and watchmaking: it is biologically inert. As it causes no immune response in humans, tantalum is completely hypoallergenic and suitable for people with sensitive skins and metal allergies. Many alloys prove problematic in this area as they incorporate metals like nickel and copper, both of which are common allergens and turn up everywhere in modern watchmaking. 316L steel uses nickel, as does some white gold. Rolex’s 904L steel that they market as “Oystersteel” contains even more nickel than 316L, to the point where some people who can tolerate 316L develop skin irritations when wearing 904L. Yellow gold, rose gold and sterling silver all contain copper, and bronze is predominantly a copper alloy. There are even some shoddy platinum alloys that use cobalt, which can trigger contact dermatitis in people sensitive to nickel.
Ceramic and titanium watches are the most common options for people with metal allergies, but both of these materials are lightweight and rather industrial in appearance, which is fine for a tool watch but lacks some refinement for more classic timepieces. The density of tantalum is equal to that of 18K gold, lending it that heavy luxurious feeling associated with precious metal. Tantalum is bluish-grey in colour and visually distinct from titanium or any of the silver-toned metals typical of watchmaking, and this unique appearance led to its first use in a wristwatch by Audemars Piguet in the late 70s. This early tantalum watch was made at the behest of King Juan Carlos of Spain, who collected Royal Oaks and wanted one in a blue toned metal. King Juan initially gave a steel Royal Oak to his gunsmith to attempt heat-bluing it using the same methods as his rifle barrels, and when that failed to achieve the desired results, he reached out to Audemars Piguet who crafted him a Royal Oak in tantalum for its natural blue hue.
By the late 80s the manufacture followed up this one-off creation with tantalum watches for the general public, including several two-tone quartz Royal Oaks with gold or steel accents, and a Jules Audemars Huitieme Tantal, a three-register automatic chronograph. An Audemars Piguet advertisement circa 1989 in German waxes lyrical about the use of tantalum for this collection:
“Tantalum is the medium, whose control demands the mastering of traditional craft and which provides fascinating possibilities of expression. Shimmering and resplendent in gray-blue with a contrast of gold that is simply unmatched and beautiful. The Audemars Piguet in tantalum: a privilege to possess it.”
Also in the late 80s, Jaeger-LeCoultre launched their first tantalum watch, the Odysseus Chronograph Moonphase. Much like the Huitieme Tantal, this watch utilised a tantalum case with rose gold accents to make the blueish tint of the rare metal stand out. The 34mm meca-quartz watch also featured a meteorite dial, playing into the theme of exotic materials. Not to be left out, Omega followed suit with their first tri-tone Seamaster in the same decade, the reference 22968000 in tantalum, titanium and Sedna Gold. In recent years Omega has reprised this model in 2018 with the Seamaster reference 18.104.22.168.99.001 and in 2021 with the Seamaster chronograph reference 22.214.171.124.03.001, both of which continue the theme of mixing three metals that are nigh-impervious to corrosion. Although these references are marketed as upscale, luxury versions of the Seamaster Professional, the increased corrosion resistance make them technically better suited to the rigors of sea exploration than their steel brethren.
Other brands with a focus on innovative materials have launched tantalum models over the years, but they are few and far between given the rarity of the metal and the difficulty of working with it. Panerai released the Luminor Marina Tantalium reference PAM172 in 2003 and followed it up with a chronograph version the following year with reference PAM192. Both are big and brooding timepieces with 44mm dials and cases hewn entirely out of heavy tantalum, an ultra-masculine approach befitting a brand who historically supplied divers to the Italian navy and boasted celebrity ambassadors like Sylvester Stallone. Another bruiser of a watch comes from Hublot in the form of the Big Bang Tantalum reference 301.AI.460.RX, which also measures a girthy 44mm. Legibility is rather poor for this reference though due to a lack of contrast, since everything has been rendered in shades of grey.
In 2009 independent master watchmaker François-Paul Journe released the grail-worthy unobtainium that is the Chronomètre Bleu, perhaps the most famous use of tantalum in high horology. Its retail value was eye-wateringly expensive for a mere mortal collector like myself, but that pales in comparison to the stratospheric aftermarket prices this timepiece has commanded ever since it was discontinued. Part of the justification for this pricing, beyond the natural exclusivity of a FP Journe timepiece, is the difficulty in producing and polishing a tantalum case by hand. The keen-eyed among you will notice that tantalum timepieces produced by other brands tend to have a matte or brushed finish. That’s no coincidence: tantalum is incredibly labour intensive to polish, due to its combination of high density and hardness. To my knowledge only Journe has been crazy enough thus far to produce an entirely polished tantalum case. If you managed to snag one before prices skyrocketed, cherish it.
There have been a few other tantalum watches from other manufactures, but these tend to be very short-run limited editions, like the 100-pieces Vacheron Constantin Quai de l’Ile reference 86050/000M-9343 and the 12-pieces Girard-Perregaux Tourbillon Bi-Axial. While gold and silver watches have been around for centuries, and platinum and white gold have become commonplace over the last century, tantalum is still exceedingly rare as a case material. Given its scarcity as the least common element in the observable universe, the machining mastery required to work with it, and the permanence granted by its unique strength and corrosion resistance, I would argue that tantalum is the most precious of all materials for watchmaking.