How the character is built
The 钅 radical marks this as a metal, and that is not a coincidence of this one character — it holds right across the table. Read the radical first and the element's state at room temperature is already settled. It is 金 (jīn) squeezed into the space beside another component — radicals change shape by position, which is why 金 is hard to spot until you know to look for 钅.
This character is used for the element and little else — you are unlikely to meet it outside a chemistry classroom.
The element itself
Lanthanum's name means "to lie hidden", given because it spent years concealed inside what chemists thought was pure cerium — an apt name for the whole family that followed it. It is soft, tarnishes in air within minutes and is one of the more abundant of the rare earths, which are collectively not rare at all; the difficulty was never finding them but telling them apart. Mixed with cerium and iron it makes the alloy in every lighter flint, which sparks because freshly scraped shavings ignite spontaneously.
Where it sits among the 118
First isolated in 1839.
In living things
Rare earths were assumed to be biologically inert until, in 2014, bacteria living in a volcanic mudpot turned out to require lanthanum outright — earlier work had hinted the metals helped, but here nothing else would do. They use it in an enzyme that oxidises methanol, where the lanthanide's larger size and stronger Lewis acidity make it a better catalyst than the calcium version everyone had studied — and cerium and several neighbours work just as well. The trick appears to be widespread among methylotrophs, including those on ordinary leaf surfaces, and the bacteria have proteins that grab lanthanides out of the environment with extraordinary selectivity. It is a rare case of a whole block of the periodic table being written into biology decades after everyone stopped looking.
Where it comes from in China
Lanthanum comes mostly from Bayan Obo, an iron mine on the grasslands north of Baotou whose ore happens to be full of rare earths. The host rock is an ancient dolomite soaked by carbonatite — a genuinely strange magma made largely of molten carbonate rather than silicate, and the kind of rock that concentrates rare earths better than almost anything else on Earth. The mine was opened as steel feedstock, and the world's largest rare-earth operation grew up around material that was, at first, simply in the way.
The full entry
For stroke order, example sentences, audio and the complete set of meanings, see the dictionary entry.
镧Lanthanum in the dictionary →Others built the same way
Every one of these carries 钅, and every one is a metal.