Pinpointing lost treasures already in museums

'Raiders of the Lost Ark' has its fair share of iconic cinematic moments, including Indiana Jones outrunning a giant rolling rock to escape a booby-trapped Peruvian temple with a golden idol, not to mention the special effects of spirits escaping from the opened Ark of the Covenant that were probably responsible for many children's nightmares in the 1980s.

But it is the final scene of the film that is perhaps the most thought-provoking, as the Ark – a "source of unspeakable power" – is sealed shut in a wooden crate and moved to a mysterious and expansive warehouse for 'top men' to study. The film finishes with a single figure wheeling the anonymised top-secret crate through row upon row of near-identical boxes, leaving us to imagine the other treasures stashed inside.

The dusty shelves and cases in museums may not be classified, but they still hold lost treasures hidden in plain sight. While it is highly unlikely that the fabled Ark of the Covenant is among them, mysterious artefacts and specimens are giving up their secrets as experts trawl the archives, choosing items wisely to study using the latest technology.

Indiana Jones is famously afraid of snakes, but even he could not fail to be impressed by the discovery of new species of reptile at the Natural History Museum (NHM) – and without setting foot in a desert or jungle. The museum in London is home to collections accumulated by scientists over the last 300 years, some of whom would certainly have shared Indiana Jones' wanderlust and strong belief that if an artefact is interesting, "it belongs in a museum!".

However, many of the NHM's 80 million objects and specimens are stored unidentified. One of the museum's staff describes the mysterious specimens as "a reservoir of biodiversity knowledge for many areas of the world which are difficult to sample now, and periods of time when ecosystems were much less damaged". So, it may come as no surprise that every year, new species are discovered among this extensive library of life.

Last year, curators and researchers described 351 new species including a 200-million-year-old fossil lizard that was hiding among the collections. Cryptovaranoides microlanius not only turned out to be a new species, but the oldest lizard known to science, pushing the origins of squamates – the group of reptiles containing snakes and lizards – back by up to 30 million years.

"I first spotted the specimen in a cupboard full of Clevosaurus fossils in the storerooms of the Natural History Museum," says Dr David Whiteside of Bristol's School of Earth Sciences. It had been collected from a quarry in Gloucestershire in 1953, but the technology didn't exist to expose the lizard's features.

A team used computed tomography (CT) scanning technology: a non-invasive and non-destructive technique that uses more than 3,000 X-ray projections taken over a 360° rotation to create 3D models of the internal and external features of specimens.

Whiteside says the technique "enabled us to reconstruct the fossil in three dimensions, and to see all the tiny bones that were hidden inside the rock". These bones revealed the reptile had fearsome jaws lined with sharp, blade-like teeth.

Indiana Jones would find a CT scanner handy if he wanted to study the mummified remains of ancient burial sites... or less fortunate tomb raiders.

Earlier this year, experts used CT scans to 'digitally unwrap' the 2,300-year-old mummy of a teenage 'golden boy' complete with 49 amulets. "Their purpose was to protect the body and give it vitality in the afterlife," says Dr Sahar Saleem, a professor at the Faculty of Medicine of Cairo University, Egypt.

The mummy had been found at a cemetery during World War One in southern Egypt but had been stored unexamined in the basement of the Egyptian Museum in Cairo until recently. The scans provide a unique insight into mummification procedures and beliefs during the Ptolemaic period, as the boy wore sandals to walk to the afterlife and had a golden tongue in his mouth to ensure he could speak in the next life.

In fact, a plethora of technology and cutting-edge techniques are being used to reveal the secrets of the Ancient Egyptians in a much less destructive way than Dr Jones's tomb raiding. For example, Raman spectroscopy provides a powerful non-destructive methodology for characterising the chemical composition of inks and pigments in ancient scrolls.

It works by shining a laser beam onto the surface of the object. Most of this light is reflected off unchanged; however, a small proportion interacts with the molecules in the material and is scattered. The scattered portion of light, known as the Raman effect, is collected to produce a spectrum. Each material has a unique spectrum associated with it and therefore each one acts as a fingerprint with which to identify materials.

The Raman effect is very small, but recent advances, particularly the development of lasers, mean that Raman spectroscopy is now widely used to analyse a wide range of materials, from gemstones to documents.

Experts at Columbia University in New York are re-examining ancient papyri already held in their Rare Book and Manuscript Library. Their work in the 'Ancient Ink Laboratory' pays special attention to black inks, most of which are based on carbon. By carefully examining the Raman spectra for these black inks they can learn how the pigments were made and the inks were prepared, as well as observing systematic changes in the observed spectra with the age of the document, which can prove useful in dating them. They have also explored the evolution of red inks in antiquity and studied polychromatic manuscripts, including a fragment from the Egyptian Book of the Dead.

Energy dispersive X-ray fluorescence (ED-XRF) – another chemical analysis technique – is probably more Indiana Jones's style, because it can be used on-site, in tombs, for example.

The technique involves aiming an X-ray beam of about 2mm in diameter at the surface of an object. The interaction of X-rays with an object causes secondary fluorescent X-rays to be generated. Each element present in the object produces X-rays with different energies that can be detected and displayed as a spectrum of intensity against energy. The positions of the peaks identify which elements are present, while the peak heights identify how much of each element is present.

ED-XRF is accurate and fast, with a result ready in a few minutes, which would prove handy to a rogue archaeologist being pursued by enemies.

Mysterious minerals, in the form of elongated crystal skulls and the glowing 'Sankara Stones', feature heavily in Indiana Jones films. While our archaeological hero relies on libraries, luck and his own wit to learn more about their powers, modern experts use technology to understand the composition of gemstones and minerals.

A new mineral called kernowite was discovered among the NHM's geological collections in 2020. The specimen was probably collected in the 1700s from a mining village in Cornwall and had been masquerading as a green variety of the traditionally blue liroconite until Mike Rumsey, principal curator of minerals at the NHM, began a study into colour variations in liroconite.

Rumsey carried out analyses to determine the chemical composition of the material. The average composition of kernowite was determined from several holotype fragments using electron microprobe analysis, which involves bombarding a specimen with a focused electron beam and analysing the emitted X-rays. His team of experts also determined the structure of the mineral by single-crystal X-ray diffraction, which is a non-destructive technique employed for determination of the atomic structure of a crystal of a certain material (compound).

"I discovered a subtle difference in its chemistry," Rumsey explains. "Overall, one part of its internal structure was dominated by iron instead of aluminium, so we found it worthy of a new name: kernowite."

Unlike the crystal skull in the 2008 Indiana Jones film, the mineral is not evidence of intergalactic, inter-dimensional beings, but it is still thought to be extremely rare.

"The specimen we have was excavated from a mine that was closed around a 100 years ago and the ground has since been built upon, so unless this mineral turns up in another location it will only ever be known from an extremely limited number of specimens likely stored unknowingly in various collections around the world," Rumsey adds.

Indiana Jones is attracted to show-stopping artefacts, from legendary items to the golden idol he tries to liberate in the first film, but he also appreciates the value of historical objects with humbler origins, such as 'the cup of the carpenter' among the glittering array of false Holy Grails guarded by the knight in the third film, 'Indiana Jones and the Last Crusade'. While Indy relies on his gut and courage to choose the correct grail 'wisely' and save the life of his father, a little technological wizardry would have helped him on his brave quest.

Now, archaeologists have a whole host of technical tools at their disposal to date objects and understand their composition. Recently, a team of experts using modern technology identified a 4,000-year-old goldworking tool kit already on display in a regional museum, which was originally discovered in 1801 among the grave goods from an important Bronze Age burial near Stonehenge.

Dr Christina Tsoraki from the University of Leicester carried out wear analysis of the stone and copper-alloy grave goods at the Wiltshire Museum in Devizes. She initially noticed gold residue on their surfaces and that some seem to have been used like hammers and anvils whereas others looked as if they were made to smooth materials. Joined by Dr Chris Standish, an expert in Early Bronze Age goldworking from the University of Southampton, she used a scanning electron microscope coupled to an energy-dispersive spectrometer to confirm that the elemental signature of the gold residues on the tools is consistent with that of Bronze Age goldwork found throughout the UK.

The team suggests the tools were used to make multi-material objects where a core object was crafted in a material like jet, shale, amber, wood or copper and decorated with a thin layer of gold sheet.

"Our research shows how much more we can find out about how past objects were made and used when we look at them with cutting-edge modern equipment," says Dr Oliver Harris, also from the University of Leicester, who led the Beyond the Three Age System project. "This helps us understand the highly skilled processes involved in making gold objects in the Bronze Age and shows the continuing importance of museum collections ."

Wiltshire Museum is one of many to have a research agenda, encouraging experts to take another look at its exhibits in a bid to learn more about them and reveal any secrets. A group of objects are being analysed at the moment. David Dawson, director of Wiltshire Museum, says: "We know that there is lots more hidden in our collections."

While it is almost certain that the Ark or the Holy Grail is not among them, and there will always be a place for exciting expeditions and fieldwork, technology means future discoveries may not be made in temples (of doom) hidden deep in the jungle, or unmapped pyramids forgotten by the sands of time, but in our local museums.

High-tech tools may be less cinematic than horse riding, plane-jacking and "fortune and glory, kid", but they make uncovering the past slightly easier and more cost-effective, probably leading to more discoveries, with no snakes, or hat and whip required.

Now to find that Ark...