Gemini: a new stable isotope tool

The Stable Isotope Facility (SIF) at BGS has just welcomed a new arrival to its mass spectrometer contingent: Elementar’s isoprime preciSION with iso DUAL and iso MULTI PREP instrument. It is designed to analyse carbon and oxygen isotopes from carbonates as well as oxygen isotopes in waters for scientific research.

The instrument

We have nicknamed our new instrument ‘Gemini’ to reflect both its nature as a dual inlet system and its dual purpose to analyse both small carbonates and water isotopes. Since being installed in April 2025, it has already analysed over a thousand samples and is able to run a range of in-house and international standards with better than 0.1 per mil reproducibility down to a sample size of 20 μg (potentially even less than 5 µg! It is very difficult to see materials at this weight). Gemini has already successfully analysed a range of sample materials including tooth enamel, foraminifera, brachiopods and clam shells for various research questions.

Testing the Gemini

As part of the initial setup, we ran a series of tests to ensure the Gemini was running well. This included a size test that looks at what the values are for one standard if we weigh it out across a range of sizes. For this test, we used an in-house standard Keyworth Carrara marble (KCM), which is a calcite. Carrara marble has been used for building since ancient Roman times because of its beauty and it’s present in many notable structures, including Marble Arch in London, Peace Monument in Washington DC, the Pantheon in Rome and grave headstones across the world — we are currently using an offcut from a stone mason. Our batch is a valuable standard for oxygen and carbon carbonate analysis not just in SIF but also in many laboratories across the UK.

Figure 3 shows the data produced during the size test. The reproducibility was better than 0.1 per mil for both δ¹³C and δ¹⁸O across a range of sample sizes, which is excellent news and conforms with the precision required for internationally reporting of stable isotope data.

Research focuses

We use carbon and oxygen isotopes in carbonates (CaCO₃) to understand more about our environment both today and in the past. Recent published work on carbonates that the stable isotope team have been involved with include:

• using brachiopod isotope composition  to reconstruct environmental variation in the (past) oceans (Crippa et al., 2025)
• identifying changes in rainfall over thousands of years using cave stalagmites in Iraq (Fleitmann et al., 2025)
• describing changes in oxygen levels in ancient oceans (Nilsson-Kerr et al., 2025)

If you are interested in reading about other research done by the Stable Isotope Facility, please visit our Google Scholar page for our publications.

If you are a potential user of Gemini, please contact the Stable Isotope Facility. UK-based researchers can apply for access through the National Environmental Isotope Facility (NEIF), which is a NERC Service and Facility and free at the point of access for successful UK applications. The next deadline for NEIF applications is 8 October 2025. Before submitting your application, it is important that you first seek the advice of staff at the facility. Further information can be found on NEIF’s dedicated website.