Minerals and crystals Lesson 50 of the geography course of Mova's primary school: 15 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: the lesson at school .
0 Rocks are made of minerals, the way a fruit cake is made of flour, sugar and raisins: a mineral is a natural solid with a fixed chemical makeup and its atoms arranged in a regular pattern. 1 When atoms line up in a repeating pattern, the solid grows flat faces and sharp edges: that is a crystal, and the pattern decides its shape, like cubes of salt or six-sided columns of quartz. 2 Sprinkle salt into warm water, leave the saucer on a sunny windowsill for a week, and tiny cubes appear as the water evaporates; crystals grow by adding atoms layer by layer. 3 Geologists tell minerals apart like detectives: how hard they are, their colour, their shine, the colour of their powder (streak) and how they break. 4 That is how they catch fool's gold, pyrite, which glitters like gold but is harder, much lighter and leaves a black streak. 5 A mineral is a natural solid with a fixed chemical makeup and atoms arranged in a regular pattern. 6 A crystal is a solid whose atoms are lined up in a repeating pattern, giving flat faces and sharp edges; in glass the atoms are jumbled with no pattern, so glass is not a crystal. 8 Quartz is one of the most common minerals, made of silicon and oxygen, and most sand is quartz. 9 Feldspar is the most common mineral group in the Earth's crust. 10 The Mohs scale ranks minerals from 1 (talc, the softest) to 10 (diamond, the hardest) by which can scratch which. 11 Geologists identify minerals by hardness, colour, lustre (shine), streak and how they break. 12 Streak is the colour of a mineral's powder, seen by rubbing it on rough white tile, and it is often more reliable than the colour of the lump. 14 Rock salt (halite) is a mineral that formed when ancient seas dried up. 15 Crystals grow when a liquid cools or a solution evaporates, adding atoms layer by layer. 16 The Cave of Crystals in Naica, Mexico, holds gypsum crystals up to about 12 metres long, which grew very slowly for hundreds of thousands of years in warm mineral water. ← previous Sedimentary and metamorphic rocksnext → Gemstones and precious metals↑ back to Geography This page in Markdown → https://md.mova.elamur.ai/free/en/corpora/school/geography/50-minerals-and-crystals/