They say, among other statistically woolly but beguiling things, that all the gold in the world could fit into Trafalgar Square in London.

That, of course, is only the stuff that we can get our hands on, the stuff of the Earth's shallow crust. Dig a little deeper - 3,000 miles deeper, to be exact - and you arrive on the fringes of the world's iron-rich molten core, filled, so they also say, with such vast amounts of gold sucked in from star dust as the Earth formed, that should it be extracted by some impossible deep-world mining outfit, it would gild the world's surface to a level of between one and four metres, depending on which geologist's conclusions you favour.

That, of course, would reduce gold's value somewhat drastically, for as King Midas found out, the ability to turn everything into gold is not the global fix-all one might imagine. As it is, even the small amount of gold on display in the eponymous new exhibition at the Palace of Holyroodhouse reeks of the beauty, rarity and prestige of a metal that, while relatively easily extracted from the ground, is devilishly rare underfoot.

It is, relatively speaking, rather rare in the Royal Collection too, the archive of over one million objects bought, collected by or given to the royal family over the past 500 or so years, from which this exhibition has been picked. "When we came up with the idea of presenting Gold a couple of years ago, we thought we'd be spoilt for choice in the Royal Collection," says curator Kathryn Jones. "Surely it was bound to be packed with gold objects! But what was surprising was that there aren't that many objects of solid gold in the collection."

That is not to say that there isn't a good dose of the requisite royal bling in the coffers. George IV, notably lavish in his spending and decorative taste, commissioned a solid gold tray for his own post-coronation banquet, its carving celebrating the King's chivalric credentials. The eight and a half kilo tray itself opens the exhibition, along with a 70cm-high book, printed in gold, one of six commemorative coronation books made for the crown heads of Europe, so profligate that it bankrupted the printer who produced it.

And yet in terms of lavish royal expenditure, it is the large crystal-toothed roaring tiger head, executed in gold on a wooden core, which truly exploits the imaginative potential of both the material and the institution which it, quite literally, supports. The brain-child of Tipu, the Sultan of Mysore in South India in the late 18th century, the life-size tiger's head was originally part of a lavish throne devised by the tiger-obsessed monarch to instil fear and respect into his subjects and his British enemies.

It was the prestige of gold, evinced by its incorruptibility and perceived purity - it does not tarnish - that ensured its popularity. "We picked things that used gold significantly or in a symbolic way," says Jones, speaking during the last days of the installation at the Queens Gallery. In an exhibition which splits its gold exhibits into three sections - Royal Gold, The Art Of Gold and Sacred Gold - the diverse objects range from gold-embossed book bindings to such curios as a copy of Queen Victoria's Highland Journal, translated into Persian and lavishly illuminated in gold paint on the order of the King of Persia, Nasir al-Din Shah. There is a watercolour in gold paint of the French 'Sun King', Louis XIV, dressed as Apollo, a set of two pen-and-ink drawings on gold paper by Cittadini, and a Renaissance altar triptych by the Sienese master, Duccio, collected by Queen Victoria's husband, Prince Albert.

Elsewhere, there is no shortage of superbly executed ephemera, from a Faberge cigarette case in three-colour gold (1903) to a set of gold Tiffany opera glasses (1893) and the numerous jewels in skilfully chased and punched gold that formed wedding day gifts for a series of royal brides down the ages.

It's a dazzling bunch, certainly, but it is, oddly enough, the simple things that linger. A conjunction of two gold cups catches the eye, one a painted representation, the other tooled from a single sheet of gold. Gold Jug (1937) is an oil on canvas by Sir William Nicholson, a shimmering execution of the play of light on the surface of a small gold cup. The superb Bronze Age Rillaton Cup (1700-1500 BC) was discovered by construction workers in the early 19th century on Bodmin Moor in Cornwall, buried in a ceramic vessel and found with a decaying skeleton and the remains of a dagger. Its warm rose-yellow gold is skilfully corrugated, as is the simple handle.

"What to me is fascinating," says Jones, "is that they are incredibly similar, despite there being roughly 3500 years between the creation of one and the other. Both artists are fascinated by that strange lustre of gold and how light is reflected on its surface." It is the simplicity of this notion, wonderfully reflected in the simple but imposing beaten gold crown, excavated in Ecuador in 1854, of the pre-Incan Canari people, that shows the absolute quality of gold that has ensured its continuing importance to diverse cultures and civilizations down the millennia.

And if you find yourself becoming covetous in the face of all this finely tooled splendour, the ugly face of avarice - a painting of a pair of 16th-century tax collectors dubbed The Misers - should ensure a return to pious contemplation.

Gold, The Queen's Gallery, Palace of Holyroodhouse, Edinburgh (0131 556 5100, www.royalcollection.org.uk) until July 26

Daily, 9.30am - 6pm (4.30pm in March) Closed, 3rd April

Adults/Concessions £6; Children/Disabled £3.30; Under 5s free