This paper describes a research project on Reigate stone, undertaken by HistoricRoyal Palaces (HRP) over the last four years. 1 Reigate Stone was used extensively at the royal palaces from the medieval period, and is infamously nondurable. Reigate Stone was replaced with more durable stones, such as Bath Stone, in the nineteenth century, but more recently there have been efforts at conservation. To date, the HRP project has concentrated on gaining a more complete understanding of the nature of the stone, which is unique in the British Isles. The project has involved re-enteringthe abandoned underground quarries in East Surrey to take core samples, which have been analysed by various techniques. Results were incomplete at the time of writing Oune 2001), but much useful new information about the stone has been gained. Comparative treatment trials have gone ahead in recent months, in collaboration with US-based researchers. Further discussions with academics and practitioners are planned.
In general, barred olivine (BO) chondrules formed from completely melted precursors. Among BO chondrules in unequilibrated ordinary chondrites, there are significant positive correlations among chondrule diameter, bar thickness, and rim thickness. In the nebula, smaller BO precursor droplets cooled faster than larger droplets (due to their higher surface area/volume ratios) and grew thinner bars and rims. There is a bimodal distribution in the olivine FeO content in BO chondrules, with a hiatus between 11 and 19 wt% FeO. The ratio of (FeO rich)/(FeO poor) BO chondrules decreases from 12.0 in H to 1.6 in L to 1.3 in LL. This is the opposite of the case for porphyritic chondrules: the mean (FeO rich)/(FeO poor) modal ratio increases from 0.8 in H to 1.8 in L to 2.8 in LL. During H chondrite agglomeration, most precursor dustballs were small with low bulk FeO/(FeO + MgO) ratios and moderately high melting temperatures. The energy available for chondrule melting from flash heating was relatively low, capable of completely melting many ferroan dusty precursors (to form FeO‐rich BO chondrules), but incapable of completely melting many magnesian dusty precursors (to form FeO‐poor BO chondrules). When L and LL chondrites agglomerated somewhat later, significant proportions of precursor dustballs were relatively large and had moderately high bulk FeO/(FeO + MgO) ratios. The energy available from flash heating was higher, capable of completely melting higher proportions of magnesian dusty precursors to form FeO‐poor BO chondrules. These differences may have resulted from an increase in the amplitude of lightning discharges in the nebula caused by enhanced charge separation.
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