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5 hits

  • Thumbnail for 865
    865

    A noteworthy characteristic of this allotriomorphic granite is the presence of feldspar laths with albite twinning in the core and anhedral k-feldspar rims. The remainder of the rock is comprised of equigranular and subhedral biotite, hornblende, and k-feldspar grains. Randomly oriented prismatic apatite grains are abundant in this sample.

  • Thumbnail for 504; 505
    504; 505

    The feldspars in this thin section are partially sericitized and somewhat poikilitic and the biotite is substantially altered. Grains are generally anhedral in shape.

  • Thumbnail for 671
    671

    This allotriomorphic granite shows evidence of weathering as most feldspars are partially obscured by a dusting of clay minerals. Tartan twinning of microcline is obvious throughout the sample. The curving of biotite cleavage and subhedral grain shapes indicates the biotite is not pristine. It is commonly found occurring with subhedral hornblende as well as large, clear to light brown, anhedral sphene crystals.

  • Thumbnail for 679
    679

    This allotriomorphic granite is dominated by feldspar phases which are altering to clays. The mica phases are anhedral, emabyed, and filled with unaligned opaque inclusions.

  • Thumbnail for 876
    876

    The riebeckite grains in this sample are embayed in a skeletal fashion, with embayments strongly controlled by the amphibole cleavage. The feldspars have classic albite and tartan twins in addition to patchy lamellae.