Mike Tuke’s

CLASSIFICATION & DESCRIPTION

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Classification and description A first look at an igneous rock A P 30 min Students are provided with a piece of granite with the different minerals clearly visible. They work out how many different minerals there are and then say what the visual properties of each are.  They then measure the grain size of each. Grouping samples  A P 10 min To help students work out what criteria are important in grouping rocks they are given a tray of 10 or so igneous rocks. Students group them using any criteria they wish but must be able to state their criteria. Grain size  A P 10 min Students are given 10 or so igneous rocks which they must put in order of increasing grain size. They must then measure the grain size of each. Classification    A P 5 min Students are provided with a simple classification table (just acid and basic and grain size) on an A3 sheet. They are also given samples of acid and basic rocks and must place each sample into its correct square using the grain size and colour. Bar graphs Pa I 30 min To familiarize students with the mineral content of each rock group Students draw stacked bar graphs for the mineral content of each rock group. Dark minerals should be shaded. Investigating the properties of igneous rocks A F P 1 hour To help students learn the mineral composition of the 4 groups students are given a table showing the modal composition of granite, diorite, gabbro and peridotite and density of each mineral. Students calculate the percentage of dark minerals and the density of each rock and see if there is a relationship. Description of samples A P F 5 min Students describe the samples using technical terms. It is sometimes helpful to provide a list of the technical terms they should be using. Interpreting samples A P 5 min per sample Students are given a variety of igneous rocks and must describe each and say how it formed.  An easier task is for students to match the samples to a list of names and a list of conditions of formation. Textures of igneous rocks A P 5 min per sample Concentrating just on the textures of the samples, students name the texture and how that texture was caused. Point counting   A P F 10 min To familiarize students with the minerals in granite and to calculate the percentage of each, students are provided with an A4 photograph of a slab of granite and a ruler. They record the mineral under the line on the edge of the ruler at each centimetre.  They should make 100 readings and then calculate the percentage of each mineral.  Quartz porphyry  A P F 45 min Students are given photocopies of a slab of quartz porphyry with a straight line drawn on the left side of it. They must measure the angle of the long axis of each phenocryst from the line and then plot them on a rose diagram. Photomicrographs 1 A I F 5 min per card Students examine a series of photomicrographs stuck onto card. Each photomicrograph has a scale and the minerals are identified. Students must work out the grain size, describe the texture and name the rock. It is helpful to give students a list of suitable terms. Photomicrographs 2 A I 5 min per sample Students are provided with a number of samples and photomicrographs from similar rocks. They describe a photomicrograph in terms of mineralogy, grain size and texture and then match the photomicrograph to the sample on the basis of texture and mineralogy. Recognizing minerals A P 20 min Students are provided with granite and olivine gabbro and labelled samples of quartz, K feldspar, plagioclase, muscovite, biotite, augite and olivine. They make simple descriptions of the visual characteristics of each mineral and then find it in the rocks. Alignment of phenocrysts due to movement  E P or D F 30min Golden syrup (=magma) sugar strands (=phenocrysts), are used to show that alignment of phenocrysts only occurs when magma moves into a narrower channel and not by movement alone.  Alignment due to settling in magma E Pa P 30 min Sugar strands are dropped into a small, clear rectangular container. From a side view they will be approximately aligned. The side can be photographed, enlarged and a rose diagram plotted of their orientation to see if the spread of alignment matches that in cumulate deposits. Alignment TE a) Due to settling: Imagine how pennies will settle after being dropped into a well. b) Due to movement: Do Poo sticks (sticks dropped into a stream from a bridge) align themselves with the flow of the water?