New certified reference material from biotite: BTNO-Nano-Pellet

Biotite Norway-Nano-Pellet(BTNO-NP) is our next certified Nano-Pellet from a mineral, which myStandards produced following the provisions of ISO 17034. Here you will learn about biotite and why we chose it to be one of our certified reference materials.

Biotite properties and its importance as a certified reference material

Biotite, also called dark mica, is one of the most common types of mica, together with muscovite. The mineral crystallises in the form of sheets and has a Mos hardness between two and three and a density of around 3 g/cm³. Biotite occurs as a rock-forming mineral in many magmatic rocks, e.g. in granites. It has the chemical formula K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂.

The mineral chemistry of biotite can be used as a powerful tool to determine the degree of differentiation of host magmas and to assess the physico-chemical conditions for rock formation. It can also be used to determine the nature of the magma source. In addition, the age can be determined by measuring the Rb and Sr mass fractions. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), for example, is suitable for analysing the chemical composition of minerals like biotite. In order for such analyses to give accurate results and thus also the correct conclusions, the analytical instruments must be calibrated with a material that is as similar as possible and has a well-known chemical composition. BTNO-NP is perfectly suited for this purpose. It consists of pure biotite, without binding agents, is matrix-matched and well characterised.

Nano-Pellets from biotite as reference material

As always, we followed our established procedure for certifying reference materials. All these steps were performed meticulously following ISO 17034 and are mandatory under this standard in order to designate a material or the values attributed to it as certified. In this way, we achieve a consistently high quality. An example of our data evaluation and the certification report with further information can be found on the BTNO-NP product page.

In the first step after planning, 250 g of biotite powder were purchased from a mineral dealer and the identity of the material was confirmed by X-ray diffraction.

Next, the powder was prepared by our team through wet grinding, freeze drying and homogenisation in our production laboratory. To divide the powder, it was processed with a rotary sample splitter, resulting in a total of 44 batches in glass vials, 28 of which were used for characterisation. For storage, the vials were vacuum sealed with silica gel and stored in a desiccator. The chemical analyses of the powder were performed in two ISO 17025 accredited laboratories.

Stability and homogeneity are measured directly on the Nano-Pellets. For this purpose, we produced a total of 47 Nano-Pellets from batch BTNO-NP-2021-10-B01 and analysed 5 of them for homogeneity with LA-ICP-MS using a randomized measurement scheme adapted to a procedure of ASTM Guide E-826-14. For two others, we simulated the delivery conditions and conducted stability tests. We also stored more Nano-Pellets in a desiccator for further stability monitoring.

In a final step, we combined the results with the characterisation evaluation ending up with certified values including their combined and expanded uncertainties for a variety of analytes, all of which are listed in the certificate.

We are always interested in Feedback: For example, if you would like to see additional elements, isotopic ratios or need further information which are not in the certificate or certification report feel free to contact us! It is also possible to press Nano-Pellets out of the remaining powders for other methods, e.g., LIBS or micro-XRF. These Nano-Pellets, because they lack a homogeneity- and stability test, will not be designated as certified, but are very well characterised for their chemical composition.

The Mica Set

With the launch of our biotite certified reference material, we would also like to introduce our Mica Set. This Set includes the three mineral Nano-Pellets MSNA-NP (Muscovite, CRM), BTNO-NP (Biotite, CRM) and Mica-Mg-NP (Phlogopite, PCM). The Nano-Pellets come as 10 mm diameter packed in a one-inch round aluminium mount. The mount is CNC machined from aircraft grade aluminium and coated with Diamond Like Carbon (DLC). It is ideal for laser ablation (LA-ICP-MS) and simplifies handling and storage.