A piece survives being handed down for unglamorous reasons. Solid metal rather than plated. Stones set in metal rather than glued. A construction that a jeweller in forty years will recognise and be able to repair. That is most of it. Plating is the single biggest reason a piece does not make it. A vermeil or gold-filled item can look identical to solid gold for several years and then wear through at the high points, and once the base metal shows there is no repair, only replating, which is not the same thing. Solid gold wears down too, but it wears down as gold. It gets softer and rounder and more obviously used, which is the quality people mean when they say a piece has patina. The other quiet failure is a hollow form. Hollow hoops and hollow chains are lighter and cheaper and they dent, and a dented hollow piece cannot be pushed back out. If you want a piece to last, weight is information.

Beyond materials there is a question of whether the piece will still make sense. A tennis bracelet, a plain band, a signet, a solitaire and a simple chain have all been continuously worn for a century, which is a reasonable proxy for the next one. Anything that depends on a current silhouette is a gamble, and that includes some very beautiful things. This is not an argument for buying only plain jewellery. It is an argument for knowing which of your purchases is the heirloom and which is the pleasure. On practical matters, ask for the piece to be documented at the point of sale. A receipt with the metal, the stone weight and the setting type is worth keeping in the box, because in thirty years nobody will remember, and an unidentified stone is treated as glass until proven otherwise. Also have it valued for insurance once. It costs little and it establishes that the piece existed.

Most jewellery bought as an heirloom is really bought as a gesture, and there is nothing wrong with that, but the two purchases look different. If you genuinely want a piece to travel, buy fewer things in solid metal and skip the plated version of the same design entirely, even though it is a fifth of the price. The plated one is a good purchase for a different reason. On stones, a lab grown diamond will hand down exactly as well as a mined one and nobody in two generations will be able to tell by looking. What will matter is whether the setting was well made. We would rather see a smaller stone in a properly built setting than a larger one in a thin mount, every time. If you take one thing away, pick the piece up before you buy it, because weight tells you more about longevity than the description does.