Black rock with green crystals

The purpose of this lab is to give you a chance to study closely a variety of igneous rocks. This lab is also a good review for the Final Exam!

Directions

Open the Igneous Rock Sample Set web site (Links to an external site.) in a new window or tab to view GigaPan Images of some samples (lettered samples). You'll be bearing in mind some of the lessons of the Minerals lab here, and establishing competence in rock identification, building a foundation for the collaborative Rock Identification and Interpretation assignment at the end of Module 08.

To complete these lab questions, use the Igneous Rock Sample Set web site rock illustrations, the Igneous Rocks Classification Key.pdf, Igneous I and II PPTs, your course workbook and Igneous chapters in your online textbook.
https://opentextbc.ca/geology/part/chapter-3-intrusive-igneous-rocks/

https://opentextbc.ca/geology/part/chapter-4-volcanism/

Grading

This part of lab exercise is required and worth 35 points. Each question is multiple choice. Choose your answer and either highlight it, circle it, make it a different font color or create a numbered list with the correct term. Do not use letters as it is not always clear which letter goes with which term.

Lab Questions

1) Zoom in on Sample A. You will see that this hand sample is composed of a very dark (black) rock that forms the "matrix" or "groundmass." Embedded within the black rock are beautiful green crystals. The green crystals are referred to as "phenocrysts." What is the overall texture of this igneous rock?

fine-grained (aphanitic) coarse-grained (phaneritic) porphyritic pyroclastic or fragmental

2) Looking at Sample A, how would you classify this igneous rock based on its composition?