China
Africa
Explore chapters and articles related to this topic
Minerals
Published in W.S. MacKenzie, A.E. Adams, K.H. Brodie, Rocks and Minerals in Thin Section, 2017
W.S. MacKenzie, A.E. Adams, K.H. Brodie
Other examples of amphiboles are illustrated in the sections on igneous and metamorphic rocks. Hornblende is also common in metamorphic rocks as well as Actinolite (Fe-rich) –Tremolite (Mg-rich), and also the blue amphiboles, especially Glaucophane (253–255). Ortho amphiboles may also be present which are colourless in plane polarised light. For example, anthophyllite is common in metamorphosed ultrabasic rocks.
Lexicon of lithostratigraphic units for the Sudan
Published in J.R. Vail, Lexicon of Geological Terms for the Sudan, 2022
The rocks are now serpentinitic and talc schists, but indicate harzburgitic and dunitic affiliation, pyroxenites and lherzolites, podiform chromite lenses, and gabbros. Associated rocks include glaucophane schists (blueschist metamorphism), basic metavolcanics with intercalated acid to intermediate volcaniclastics, cherts, and pelagic sediments and shallow water sediments.
A review of the occurrence of and potential for jade in the New Guinea Mobile Belt
Published in Australian Journal of Earth Sciences, 2022
Chloromelanite blocks from upper Torare River, between Lake Sentani and Jautefa Bay, west of Humboldt Bay (=Yos Sudarso) (Figure 10) were used in the manufacture of adze blades and other implements. Some tools were traded widely, including across the Bismarck Archipelago to Emirau Island, a small coral island (localities b, c, s, Figure 1 and Table 1; Harlow et al., 2012; Wichmann, 1901a, 1901b, 1917 ). van der Wegen (1971) considered the green jadeite-rich pyroxene present in a chloromelanite adze blade from Genjem, 25 km west of Lake Sentani, to be a jadeite-rich, acmite-poor chloromelanite. However, Harlow et al. (2012) considered the chloromelanite to be jadeitite. The chloromelanite rocks from Torare River occur intercalated with amphibolites probably representing metamorphosed gabbroic rock (Wichmann, 1901a). These rocks crop out in an east–west-elongated 65 × 20 km ultramafic body, dissected by east–west faults (Dow et al., 1986). Ultramafic rocks include amphibolite and gneiss with talc-schists and schistose serpentinites, likely remnants of peridotite and dunite (Baker, 1956; van der Wegen, 1971). Blueschist assemblages comprising chloromelanite–glaucophane–epidote–albite–white mica–garnet are developed in metamorphic rocks including epidote–albite schists, sericite–albite schists, actinolite schists, calc-phyllites, marble and quartzite (van der Wegen, 1971).