Reading Earth Materials

Overview

Students investigate how minerals, crystals and fossils appear in rocks, then use observable properties to infer possible human uses. The lesson uses Aotearoa New Zealand examples, including granite, limestone, coal, petroleum, salt, mica and the work of geomorphologist Charles Cotton.

Prior knowledge: Students know that rocks occur naturally in the landscape and can describe basic visible features such as colour, texture and hardness. Clarify that a rock is a naturally occurring mixture or mass of minerals and may also contain fossils; a mineral is a natural material with a repeating internal pattern and characteristic properties. Not all rocks have the same composition.

Learning intentions

Students will:

• describe minerals, crystals, rocks and fossils using observable evidence
• distinguish a rock from a mineral and explain that rocks can contain more than one mineral
• classify samples or images by their properties and justify classifications
• infer why particular earth deposits are useful for particular purposes
• recognise how Charles Cotton contributed to understanding New Zealand landforms.

Success criteria

• I can describe at least two observable properties of a sample.
• I can explain the difference between a rock and a mineral.
• I can use evidence to classify a sample and explain my decision.
• I can link a property, such as strength, density, shine or absorbency, to a possible use.

Curriculum links

• Earth Systems focus: minerals are natural materials with repeating patterns that give them unique shapes and properties.
• Rocks and minerals: rocks are made of minerals and crystals and sometimes contain fossils.
• Earth deposits have observable properties and are used according to those properties, including iron, aluminium, salts and mica.
• The study of New Zealand landforms and geomorphology, including the contribution of Charles Cotton.

This lesson aligns with the New Zealand Curriculum Refresh through disciplinary science practices: observing carefully, classifying, using evidence, communicating explanations and connecting science knowledge with people and place. The aligned official descriptor is Recognising and describing the makeup of Earth materials to explain how minerals, crystals and fossils appear in rocks, alongside the related rocks-and-minerals descriptors above.

Lesson structure (60 minutes)

1. 0–5 min · Local hook. Display the opening images of a New Zealand beach, a road-cut and a crystal sample and ask: “Are these all rocks? What evidence would help us decide?” Students make an individual prediction, then share one observation with a partner.

2. 5–15 min · Build the model. Use the concept slides showing minerals, crystals, rocks and fossils to teach: minerals are natural materials with repeating patterns; crystals show orderly growth or structure; rocks may contain one or several minerals, crystals and sometimes fossils. Introduce coal and petroleum as natural earth deposits with observable properties. Ask: “Can a rock be made of different minerals?” “Would every piece of rock have the same composition?” “What evidence would suggest a fossil is present?” Students add definitions and a labelled sketch to the Earth materials investigation sheet.

3. 15–20 min · Model observation. Demonstrate a safe close observation of one sample or image without naming it. Think aloud using colour, lustre, grain size, visible crystals, layers, pores, hardness evidence already provided and possible fossil markings. Model the distinction between observation (“I can see pale grains”) and inference (“It may contain more than one mineral”). Students practise turning one observation into an evidence-based inference.

4. 20–42 min · Hands-on classification investigation. In five groups of five, provide trays of labelled rock/mineral samples or clear images, hand lenses and an observation table. Reopen the investigation instructions and property prompts. Students observe, sketch or photograph where permitted, record at least three properties, and classify each item as likely mineral, rock, earth deposit or uncertain. They must justify one classification using “I think… because I observed…”. Circulate and ask: “What is your evidence?” “Could this be a rock containing several minerals?” “What might the repeating pattern in a crystal explain?” “Which observations are reliable without testing?” Students complete the investigation section of the Earth materials investigation sheet.

5. 42–54 min · Uses and Aotearoa connection. Show the property-to-use slides featuring iron, aluminium, salt, mica, coal and petroleum. Explain that iron is strong and dense, while aluminium is strong and less dense; these properties influence uses. Salt is useful as a food ingredient and preservative, and mica’s layered, heat-resistant and shiny properties have supported electrical and industrial uses. Introduce Charles Cotton as a New Zealand scientist who advanced the study of landforms and geomorphology between 1885 and 1970. Ask: “Why might a lighter strong metal be useful for transport?” “What landform evidence might help explain how a place formed?” Groups select one deposit, identify an observable property, propose a use and give a short evidence-based explanation.

6. 54–60 min · Consolidation and exit ticket. Return to the hook using the final recap and discussion slide. Students complete the final three questions on the Earth materials investigation sheet: define a mineral, explain why a rock may contain different minerals, and link one deposit’s property to a use. Collect sheets and invite two students to share answers.

Resources

• the Earth materials and investigation slide deck
• the Earth materials investigation sheet
• Sets of labelled rock and mineral samples, or high-quality images
• Hand lenses
• Trays, pencils, rulers and coloured pencils
• Optional balance and water-resistant table covering
• Safety goggles and damp cloths for cleaning

Assessment

• Listen for accurate use of “mineral”, “rock”, “crystal”, “fossil” and “earth deposit” during questioning and group explanations.
• Check investigation tables for three observations, a justified classification and recognition that rocks may have different compositions.
• Use the exit ticket to identify students needing reteaching about rock/mineral distinctions or property-to-use reasoning.

Differentiation

• Provide a word bank, labelled sample cards, sentence frames (“I observed… therefore I think…”) and a partially completed table for students needing support.
• Allow students to record observations through labelled drawings, oral explanation or a scribed response; use enlarged images and tactile samples for students with visual or motor needs.
• Pair multilingual learners with supportive peers and pre-teach the vocabulary with real objects, gestures and simple definitions.
• Challenge students to classify an uncertain sample in two possible ways, identify further evidence needed, or compare why iron and aluminium suit different applications.

Teacher background notes

A mineral is naturally formed and has an organised, repeating internal structure; visible crystals are evidence of that structure but are not required for every mineral sample to look like a large crystal. A rock is an aggregate or mass of one or more minerals and can include organic remains or fossils. Coal and petroleum are natural earth deposits formed through geological processes; avoid presenting them as minerals. Do not ask students to scratch samples or taste minerals. Use only teacher-approved, clean samples, supervise handling, and wash hands after the investigation.