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Troctolite P79
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Pa18 Trachyt
A gray igneous rock with a porphyritic texture. It includes a few phenocrysts of feldspars and dots of black material; probably micas.
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Troctolite
The rock found using IUGS classification with normalized mineral modes in steps 2 and 3. Composed of plagioclase and olivine mainly, with other inclusions of magnetite, pyrite, and biotite.
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PA45 Granite
MEGASCOPIC: A gray, medium-grained rock consisting of feldspar, quartz, biotite, and muscovite
MICROSCOPIC: Subhedral-granular with euhedra sodic plagioclase whereas quartz and feldspar are anhedral. Magnetite and minor sphene are the other accessories along with trace mincropegmatite. In addition to some sericite, a small amount of secondary epidote is present.
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Phonolite
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Olivine Gabbro (1830)
Macro: Hand specimen is medium-grained dark gray rock, over 90% of the rock is made up of about equal amounts of plagioclase and pyroxenes, with the rest made up small olivine grains and possibly magnetite.
Micro: Thin section show large amounts of well twinned plagioclase. Augite/diopside also common showing good cleavage, but they are largely anhedral. Small olivine grains within pyroxenes.
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Monzonite (R1822)
Location: Silverton Calorado
Geologic Age: Miocene
Macrodescription: A purplish-gray rock consisting chiefly of plagioclase, orthoclase, and greenish hornblende with small amounts of quartz
Heterogranular texture with a few large cloudy orthoclase crystals with poikilitic plagioclase and mafic inclusions. Some potash feldspar has rims of granophyre which also forms interstitial patches. Dominant plagioclase ranges in size considerably and shows gradation zoning. Augite is partly or wholly uralitized to very weakly pleochroic green hornblende. Biotite is in part chloritized. Coarse granular magnetite is common; apatite and zircon are rare.
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Pty 8 Monzonite, Malgoda, Predazzo, Tirol
A tan monzonite (possible biotite)
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Trachytic Texture
The trachytic texture is reflected in the oriented nature of microlites around the embayed plagioclase phenocryst. This distinct orientation suggests a flow direction, the movement of microlites around the larger grain.
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Microphenocryst
Microscopic crystals that are still larger than the remainder of the groundmass
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Sieve Texture
Sieve structure is composed of deep and irregular embayments. The cause of this structure is debated to be due to advanced resorption or from rapid crystal growth enveloping a melt.
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R1803 & PET-1: Phaneritic Granite
Anhedral is a textural term used to describe crystals that lack characterisitic faces. Anhedral crystals are not necessarily irregular in shape, but could be closely packed together which would dictate crystal face formation.
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Embayed Texture
A bay-like formation caused by a reaction with the melt (resorption). Resorption is the re-fusion or dissolution of a mineral back into a melt or solution from which it formed.
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R1841: Green phaneritic Dunite
This thin section displays the igneous equigranular texture. This entails that most of the crystals in the slide have a similar size within a reasonable range.
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Orbicules
This sample is an orbicular granite. Varying in size, their shapes are ovoid masses of radiating crystals, commonly concentrically banded, found in some granites.
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Felty or Pilotaxitic Texture
A chaotic or random arrangement of microlites
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Xenolith texture
This rock displays a xenolith of Dunite (Olivine) in vesicular basalt. A xenolith is a rock inclusion, in this case from the mantle.
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PET-1: Myrmekite Texture
Worm-like quartz intrusions in plagioclase feldspar
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Fiamme and Pyroclastic Texture
Fiamme – a piece of pumice that has been severely compressed by the weight of the overriding volcanic material in a deposit. They appear as long, black and “lense-shaped” fragments in the deposit
Pyroclastic – texture composed of many different types/shapes of volcanic debris, created during an explosive eruption.
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Pipe Vesicles
Pipe vesicles are holes in extrusive igneous rocks. They form as gas filled lavas reach the surface and the gases in the lava expand coming out of solution and escape upwards.
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P169: Trachyte, Mt. Dore, Auvergne, France
Grey, porous rock, with phenocrysts of sanadine, black, shiny plates of mica and dark-green crystals and grains of augite
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P193: Dacite, Rigel, Kohlbach, Hungary.
Red Dacite
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P59: Quartz-Diorite (Tonalite), Adamello
White/Black, Coarse Grained, Quartz, Diorite
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P220: Basalt, Stempel, Marburg, Hessen
Blueish-Black, Fine Grained Olivine, Basalt
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P192:Dacite, Vichne, Schemnitz, Hungary
Quartz Diorite