Britvinite, Pb15Mg9(Si10O28)(BO3)4(CO3)2(OH)12O2, a new mineral species from Långban, Sweden

Molybdophyllite: crystal chemistry, crystal structure, OD character and modular relationships with britvinite

“…Britvinite sample 740945 is biaxial negative, with mediumÀsmall 2V (roughly 10À20º) and r < v weak. These properties are in agreement with the data reported for type britvinite (Chukanov et al, 2008). Molybdophyllite sample 221135 is also biaxial negative, the 2V value is very small (<5À10º), and the optical axis figure has a strongly pseudo-isotropic character.…”

“…The results for britvinite sample 740945 obtained in the present study (composition 5a in Table 1) compare well with those given by Charalampides (1994) for molybdophyllite-18 Å (5b) and by Chukanov et al (2008) for type britvinite (6); these last authors proposed the ideal chemical formula Pb 15 Mg 9 (Si 10 O 28 )(BO 3 ) 4 (CO 3 ) 2 (OH) 12 O 2 .…”

“…(1) Sample 740945 (britvinite): the multiple bands at 3694 cm À1 (s),~3658 cm À1 (s), 3579 cm À1 (s), 3520 and 3495 cm À1 (both s) and~3400À3160 cm À1 (very broad shoulder) are all assigned to absorptions due to OH stretching vibrations in hydroxyl groups; the weak band at 2780 cm À1 may have the same origin but is left unassigned, as is the band at~2450 cm À1 (s, b); the strong bands >3100 cm À1 are very similar to those reported for type britvinite (Chukanov et al, 2008) where the IR spectrum has three weak bands at 3685 (sharp),~3570 (broad) and 3440 cm À1 (very broad). The britvinite spectrum has no other absorption features in the region between~3200 and 1500 cm À1 .…”

“…We have also carried out a data collection on a crystal of britvinite from sample 740945, followed by structure determination and refinement which confirmed the general aspects of the structural arrangement obtained by Yakubovich et al (2008) for britvinite, with some distinctions in structural details and in the crystal-chemical interpretation. Our structural study of britvinite will be presented in a future paper, which will include new chemical analyses of the light elements (B, C, O, H) and a detailed discussion of the results and comparison with those obtained by Yakubovich et al (2008). In the present paper, which is primarily devoted to the results obtained in our study of molybdophyllite sensu stricto, we discuss only those aspects of britvinite that are useful for a better understanding of the modular relationships between the two minerals.…”

“…The species forms colourless to pale yellow, very pale green or pale grey micaceous aggregates, which are flexible and only a little 85.75(3) and g = 60.10(3)º. In fact, whereas these parameters correspond to the reduced cell, this is not true for those presented by Chukanov et al (2008), which have to be transformed via the matrix [1 À1 0 / 1 0 0 / 0 0 1] to give a = 9.332, b1= 9.341, c = 18.833 Å , a = 75.82, b = 85.56 and g = 60.17º. The agreement between the two sets of parameters is excellent, especially taking into account the fact that the data presented by Chukanov et al (2008) were obtained at low temperature (173 K).…”