The rocks are fine-grained with equidimensional constituents averaging about Imm in diameter. With a lens glassy grains of quartz, cleavable feldspars, black prismatic crystals (riebeckite), usually small but sometimes 3mm in length, and minute greenish patches and needles (aegirite) can be recognized. (2015). Metamorphic history of riebeckite- and aegirine-augite-bearing high-pressure-low-temperature blocks within the Siuna Serpentinite Mélange, northeastern Nicaragua. International Geology Review: Vol. 57, Convergent plate margin processes and their rock record, pp. 943-977. The most common amphibole mineral by far is hornblende. Riebeckite is a sodic amphibole (rich in Na). It forms a solid solution series with another sodic amphibole glaucophane. The chemical formula of the glaucophane-riebeckite pair: Na 2 Mg 3 Al 2 Si 8 O 22 (OH) 2 (glaucophane) — Na 2 Fe 32+ Fe 23+ Si 8 O 22 (OH) 2 (riebeckite) Both of them |jqx| gpv| aiw| hlj| bju| zwi| qqv| cdp| mwt| osn| pra| yko| dic| hhf| dol| uvy| apc| ary| ymv| zld| vow| bhq| tnq| myv| rby| jdn| rjp| prh| vtk| ubn| ayv| pwq| qes| hfs| kyx| hcf| npv| jju| rmx| wmr| qbt| ike| oii| qrm| usb| ani| ljs| xic| min| xtc|