Certification of Iceland Tholeiitic Basalt <scp>IAG BNA</scp> ‐1 Using the <scp> Geo <i>PT</i> </scp> Proficiency Testing Certification Protocol

The certification protocol developed for the Geo PT proficiency testing programme was applied to the certification of Iceland Tholeiitic Basalt IAG BNA‐1. Certified values for eight major element oxides and twenty‐nine trace elements were reported together with fourteen indicative values. Metrological traceability was demonstrated in part by the excellent agreement between Geo PT assigned values and certified values for the established certified reference material BRP‐1 (Basalt Ribeirão Preto), which was distributed for co‐analysis with BNA‐1 in Round 54 of the Geo PT programme. A comparison shows clear similarities, but some differences when the composition of BNA‐1 was compared with values for USGS BIR‐1 (Reykjavik Iceland Basalt), which originated from the same quarry near Reykjavik in Iceland. An assessment of quality factors for IAG BNA‐1 shows that BNA‐1 certified values are fully compatible with usage involving the assessment of data submitted by laboratories that routinely analyse silicate rocks to the Geo PT ‘research laboratory’ standard of performance.