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53 hits

  • Thumbnail for SS-3674-3
    SS-3674-3

    The largest crystals in this sample are augite, in which twinning is common, as is alteration to a mixture of chlorite and biotite, and the formation of glomeroporphyroclasts. Chlorite and biotite also are found rimming olivine grains, which are themselves clustered with augite and biotite crystals. The mafic phases are typically subhedral in shape, in contrast to the nephaline, k-feldspar, and zeolites which are anhedrally intergrown together in the interstices between augite crystals.

  • Thumbnail for 484
    484

    Perthitic intergrowths of k-feldspar and albite are prevalent throughout this coarse-grained, nearly allotriomorphic granite. Riebeckite and biotite are found intergrown together in anhedral masses. The rare tiny, equant olivine crystal is observable.

  • Thumbnail for CF1B
    CF1B

    The olivine phenocrysts in this vesicular basalt are unaltered, in contrast to the second phenocrystic phase, plagioclase, which has a speckled, mottled alteration texture encroaching concentrically inwards from the grain boundaries. Only the cores and a thin corona of plagioclase on the outermost edges of the phenocrysts remains unaltered by this opaque phase. The glassy groundmass contains of unoriented plagioclase microlites and tiny olivine crystals. Olivine phenocrysts are smaller and less abundant in CF1B than CF1A. Plucking of olivine crystals is extensive.

  • Thumbnail for CM4
    CM4

    The vesicles in this microporphyritic vesicular basalt are substantially smaller than the other Carr Mountain samples, though composition remains similar. More calcite permeates the groundmass, in which plagioclase microlites are visible. Unaltered augite and olivine microphenocrysts are observed. An isotropic zeolite, presumably analcite, is seen infilling several vesicles.

  • Thumbnail for B2
    B2

    The outer rim phenocrysts of augite and olivine, though the red stain, which concentrates in the glass and olivine phases, obscures the characteristic birefringence of the olivine. Plagioclase microlites are present in the glass and calcite has infilled some pore spaces. The core of this bomb appears to be hematite and glass cemented tiny quartz crystals.

  • Thumbnail for CM2A
    CM2A

    Augite and olivine are the two predominant crystalline phases in this vesicular basalt and define a microporphyritic fabric. Iddingsite replacement of olivine is minimal. As smaller crystals, both phases, along with opaques, a feldspar, and glass, comprise the groundmass.

  • Thumbnail for BATUR 94 CR
    BATUR 94 CR

    Sieve textured plagioclase blocks and laths dominate the phenocrystic population in this microporphyritic vesicular basalt. Clinopyroxene phenocrysts are less abundant and olivine less abundant still. All three phases are found in the groundmass. Groundmass clinopyroxene and olivine are more abundant than in BATUR 94 FL.

  • Thumbnail for BATUR 1918
    BATUR 1918

    Subhedral phenocrysts of plagioclase, clinopyroxene, and olivine are scattered randomly throughout this basalt. Plagioclase has a sieve texture and is frequently zoned. The corners of most grains are rounded. Both clinopyroxene and olivine are generally equant in shape and olivine is more abundant than the pyroxene. All three phases show some degree of resorption. The groundmass contains moderately-sized crystals of all three phases. This sample is very fresh and unaltered.

  • Thumbnail for 58-K-91
    58-K-91

    Unoriented plagioclase laths and interstitial glass and clinopyroxene make up the groundmass of this vesicular basalt. Olivine and orthopyroxene microphenocrysts are scattered throughout.

  • Thumbnail for 867
    867

    This mineral phases in this gabbro are highly fractured and frequently embayed. The pyroxenes are roughly euhedral in shape and several equant grains are twinned. The opaques in this sample are typically equant in shape and contain inclusions of olivine or a fiery orange-red mineral that appears the same in plane- and cross-polarized light.

  • Thumbnail for SS-13
    SS-13

    This porphyroclastic thin section has a groundmass dominated by k-feldspar and zeolites, though other phases may be present in lesser amounts. The phenocrysts are euhedral augite and olivine, which are frequently found clustered together in glomeroporphyroclasts. The olivine is consistently rimmed by iddingsite and the augite frequently displays concentric zoning. Tiny crystals of equant apatite and rounded opaques thoroughly pepper the thin section.

  • Thumbnail for PS-3a-PW
    PS-3a-PW

    Serpentine comprises the bulk of this thin section, with skeletal masses of clinopyroxene and isolated granules of olivine dotting the characteristic serpentine mesh-work. The pyroxenes are larger and more complete than the olivine crystals.

  • Thumbnail for Bs
    Bs

    The outer rim of this bomb is glassy with vesicles and augite and olivine phenocrysts. Small, widely dispersed plagioclase microlites are also present. The core of the bomb contains a porous aggregate of fragmental quartz held together by glass.

  • Thumbnail for SS-5
    SS-5

    Biotite and olivine dominate this sample. The olivine is frequently twinned and highly fractured. In the interstices between olivine grains grows large, anhedral biotite grains. Both phases have a sieve-like, pock-marked appearance. Rutile and opaques, all equant in shape, are plentiful.

  • Thumbnail for SW6
    SW6

    Large, anhedral, interlocking crystals of olivine and clinopyroxene are found in this coarse-grained rock. Olivine alteration to iddinsite is confined to fractures which pervade the rock and cross-cut both mineral phases. Perthitic pyroxene intergrowths are observed. A contact between an ore-rich, opaque zone and the peridotite is preserved in the thin section.

  • Thumbnail for PS-3a-occp
    PS-3a-occp

    Olivine clinopyroxenite cumulate with postcumulus (intercumulus) plagioclase.

  • Thumbnail for KBR1
    KBR1

    The dominant texture in this gabbro is an ophitic intergrowth of equant plagioclase laths within larger, subhedral, clinopyroxene grains. Alteration of some phases to chlorite, talc and clays is localized and occurs more in non-ophitic sections of the rock.

  • Thumbnail for BATUR 1936
    BATUR 1936

    Subhedral phenocrysts of plagioclase, clinopyroxene, and olivine are squeezed into the fine web of rock that rims the massive vesicles of this scoria. Plagioclase has a sieve texture and is frequently zoned. The corners of most grains are rounded. Both clinopyroxene and olivine are generally equant in shape and olivine is more abundant than the pyroxene. All three phases show some degree of resorption. The groundmass contains moderately-sized crystals of all three phases. This sample is very fresh and unaltered.

  • Thumbnail for dunite
    dunite

    Granular olivine crystals with virtually no alteration and few fractures. Great for obtaining interference figures.

  • Thumbnail for PS-1b-bs
    PS-1b-bs

    The groundmass of this basalt is composed of plagioclase microlites with tiny interstitial clinopyroxenes. Vesicles are infilled with chlorite and quartz. The few larger plagioclase phenocrysts have been partially altered to calcite.

  • Thumbnail for SG1A
    SG1A

    Plagioclase laths of varying sizes and orientations represent the bulk of this thin section. Augite is present, though in noticeably smaller quantities and olivine only in trace amounts. Tiny opaques pervade the sample.

  • Thumbnail for SG2A
    SG2A

    Plagioclase microlites and small rounded crystals of augite and olivine define this thin section. The interstices between crystals are filled with reddish-brown glass.

  • Thumbnail for JPN-13
    JPN-13

    As is characteristic of a harzburgite, this sample is greater than 90% olivine, with a few large clinopyroxene grains, fracture-infilled serpentine, and occasional, moderately-sized rutile grains making up the remaining constituents of the rock. Serpentinization is minimal.

  • Thumbnail for JPN-18
    JPN-18

    The largest crystals in this sample, visible in handsample, are clinopyroxene, much of which has strong exsolution lamellae. Much smaller are the olivine crystals, which have subsequently been broken into a serpentine-framed mosaic of optically-continuous fragments.

  • Thumbnail for 57-K-91
    57-K-91

    This vesicular basalt contains microphenocrysts of olivine and orthopyroxene, both of which are also lesser components of the groundmass which consists mainly of uniformly-sized plagioclase laths. The olivine phenocryst have weak reaction rims. Some plagioclase is zoned and sieved.