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0 B N{ 5GUC .l 62% = Fall 2022 GEL 109 Name: Lab: IGNEOUS ROCK ANSWER SHEET Table 1. Igneous rock sample identification SR Color/Shade = Dominant | Texture Rock | How did the rock | Sample Felsic, Minerals | name form? Intermediate, [ [ i or Mafic $ ‘ j V Silver (e\dsear n | OYEN \JoIC 0rias M | ‘)\)n\\(c |erP® ok | | < (X e Basolt |crwst ' " D hvelitt ) . ¥l ConrS | 3 AMA "Vf; qramyy | GV e for below o oo il FLANNGEES) BV ST , — Hornblende | Coarse- | Gabbro | As magma cooled Olivine grained | below the surface | - intrusive r\“,lr,fi( Py X Questions: Which two igneous rock samples (give their sample number and name) from numbers 8- 14 have a unique spongy looking texture? How did this appearance form? What type of igneous rock is produced by magma that cools deep below earth’s crust? What type of texture do these rocks show, and why? . o IN+r ! What type of igneous rock is produced by lava that cools on the surface of the earth? What type of texture do these rocks show, and why? - rx Fall 2022 GEL 109 4 Go back to the minerals of our kit (from the mineral lab) to find two types of feldspar One is referred to as potassium feldspar (#1, also called “microcline”), and the other is plagioclase feldspar (#2, also called “albite”). Feldspar is one of the most abundant mineral groups in the rocks of earth’s crust. Granite, for example, typically contains potassium feldspar or microcline, which are both feldspar varieties. Look at the mineral composition row of the igneous rock identification key. Potassium feldspar is more common in felsic rocks, and plagioclase feldspar is more common in mafic rocks. Consider Bowen'’s Reaction Series; how does the formation of potassium feldspar differ from the formation of plagioclase feldspar? cNOLY S The Olagizciase Jfeldspey 100€ 2 @l (L J‘ morc Mmore «Z2 M 5. What is the approximate thickness of your thumbnail using the metric system? _i_ Now when you're doing geology outdoors, you can use your thumbnail thickness as a measuring tool! Fine grained igneous rocks contain minerals smaller than the thickness ofa thumbnail, which is about 1mm.