Did it come from space? Can it really be one billion years old? No wonder this extraordinary gem, weighing about as much as a banana, is called The Enigma.

At 555.55 carats, the ancient black rock coming up for sale at auction is said to be the largest cut diamond in the world, with 55 faces, and is expected to sell for more than £4.4 million as I write.

It is certainly a phenomenon and one of the oldest items ever to come up for auction, although it is a mere youngster compared with the four billion-year-old meteorite that sold at auction in 2017 for a rather more modest £14,000.

As is widely known, diamond is one of the toughest substances known to man, having been forged deep within the Earth’s crust under intense heat and pressure so that the carbon atoms crystallise.

They are rare because so many of them remain hundreds of kilometres beneath the surface, although some emerge via magma.

Even rarer is the carbonado, black diamonds like this one that are especially tough and have only been found in Brazil and the Central African Republic.

So if diamonds are forged

In the bowels of the Earth, how come they think this one came from outer space?

Apparently it is because it also contains osbornite, or titanium nitride, a mineral so far found only in meteors. Perhaps, though, the osbornite was captured by the bubbling early planet when a meteorite crashed into it, then was transformed into the carbonado as the crust cooled and processed it. If so, The Enigma is documentary evidence of our home world’s earliest days.

It’s fascinating to see how changing social and intellectual values directly affect changing monetary value at auction.

Traditionally, craftsmanship, classic design and artistry stood at the forefront of sales in the form of Regency furniture, Georgian silver, as well as Old Master paintings and drawings.

Today, while Old Masters are still highly valued at the top end, changing tastes and dwindling supplies of the best material mean that these disciplines have faded into the background when it comes to bidding.

Replacing them are the bright, brash new designs of leading fashion brands and digital art and its associated features. Trainers (in the US: sneakers) now command five- or even six-figure prices, with collectors displaying them proudly in stacked perspex boxes. Designer handbags by Gucci and Birkin change hands for eye-watering sums, while NFTs, still so loosely understood by many of those swooping down to acquire them, sell for millions.

Status has always been a driving force behind the acquisition of high-end art and objects – nothing shouts rich and successful like having a Warhol or Van Gogh on the wall – but what has become the cult of self in society today, with its social media influencers, reality TV and celebrity culture, has helped shape what has become most desirable in the salerooms.

What will come next? Will there be a backlash against all this self-indulgence? Perhaps we will return to some of the more traditional values, and with that overlooked gems such as Victorian watercolours may come back into vogue…

Everyone must have had the dream of finding something valuable in their attic or cellar. But now, with all the TV programmes, from Cash In The Attic to Fake or Fortune, we must have arrived at a time when there can be nothing left to find?

Don’t be too sure. As reported in the past week, an auctioneer trawling through the contents of a dusty old garage in Bath recently came across several treasures: an autograph book dating back around 120 years and containing the signatures of no less a cricketing celebrity than W.G. Grace and other greats from the crease; and several letters handwritten by Grace himself from the mid to late 1890s.

What’s more, the provenance was impeccable: they came from the estate of John Douglas, who played the great game with Grace and his son.

The autograph book also contains the names of players from the touring sides of Australia and the West Indies.

The letters were written to Edward, Lord Somerset and discuss life at the time around Bath and Bristol, hunting, shooting and, of course, cricket.

The autograph book took a cool £11,600, while the letters totalled £1,000.

Still think it’s not worth digging about in the dust and cobwebs?

The Beano, The Dandy, Valiant, Eagle and Whizzer & Chips were all weekly comic thrills from the 1930s, 40s, 50s and 60s onwards. Bought for a few pennies, they livened up the end of the week, just as youngsters were preparing for the Saturday morning trip to the cinema for a programme of westerns, cartoons and the like.

Characters like Desperate Dan, Korky the Kat, Billy Whizz and the Bash Street Kids were our heroes as we chuckled at their adventures. What we never thought then, as we crumpled the weekly issue and discarded it in the bin, was that we were chucking out a fortune in future collectables.

It’s not so long ago that a first issue of Action Comics from June 1938 broke the auction record for a comic at over $3 million – the cover unveiling Superman for the first time. Additional copies of this rarity followed suit at even higher prices, while other heroes also made their mark in the millions, culminating in $3.6 million for Spiderman’s first appearance in 1962.

Now, however, this frenzied world of collecting has gone one better, with a $3.4 million bid for a single original drawing for a Spiderman comic. Dating to 1984, it shows the webbed wonder clad for the first time in his figure-hugging new black suit.

Even that’s not the record, though. A single original drawing from Tintin and The Black Lotus, by Hergé, took the equivalent of $3.8 million in Paris a year ago.

Where will it all end? Probably with prices soaring a great deal higher now so many of the new multi-millionaires and billionaires are in their twenties and thirties and grew up on this fodder.