Magnetic minerals in rocks usually record the external magnetic field during their formation, resulting in a remanent magnetisation. This magnetic remanence can be acquired as the minerals grow at ambient temperatures as a chemical remanent magnetisation (CRM). This thesis aims to quantify CRMs, with a focus on determining the strength of the field (palaeointensity) recorded during CRM acquisition. Determining palaeointensities from CRMs is important in meteoritic studies since many primitive meteorites recorded early Solar System magnetic fields as CRMs. Quantifying these fields is critical for understanding Solar System formation.

I developed a CRM model and used it as the basis for a CRM palaeointensity method. This method is the first to consider magnetic properties and acquisition conditions by modelling CRM acquisition for individual samples.

A theoretical investigation using the CRM model predicts that CRM behaviour varies significantly with magnetic properties and acquisition conditions, such as growth rate. This investigation demonstrates that in traditional palaeointensity methods, which assume that a sample's magnetic remanence was acquired during cooling, CRMs exhibit anomalous behaviour, typically leading to the rejection of incorrect palaeointensities by the current selection criteria within these traditional palaeointensity methods.

I conducted a study on natural CRMs from historical salt marsh sediments that found the sediments recorded a magnetisation direction indistinguishable from the Earth’s field. This is the first study to directly demonstrate that natural CRMs reliably record field direction.

I tested the CRM palaeointensity method on natural and experimental samples. Most estimates underestimated the palaeointensity, which I attribute to strong magnetic interactions within magnetic grain clusters likely present in the tested samples, which are not incorporated into my CRM model. The method's internal check for suitable behaviour successfully rejects most of these incorrect estimates.