‘Let’s Rock: Crystals’
‘Let’s Rock: Crystals’ by Richard and Louise Spilsbury
1. Crystals are solid structures that have definite shapes with sharp, clear edges and corners. Salt, snowflakes and rubies are types of crystal.
Crystals are minerals that have had the chance and space to grow into a particular shape. Minerals are natural substances that formed inside or at the surface of the Earth. If minerals form in spaces where there is not a lot of room, they may not have a crystal shape.
2. Water dripping through the roofs of caves contains the mineral calcite dissolved from the limestone rock. The calcite crystallizes when water evaporates from this solution. Sometimes crystals of calcite build up over time into amazing hanging structures called stalactites. The crystals may also grow into tall stalagmites where calcite solution splashes on to the floor of the cave.
3. Today, miners use powerful digging machines and drills to dig underground in search of crystals. They create tunnels held open with strong metal supports so they can keep mining ever deeper.
Diamond miners pour crushed kimberlite rock sludge down a slope covered in grease. Only the diamonds stick to the grease.
4. Some scientists do not need to find or mine crystals because they grow their own. Usually, they grow crystals from strong mineral solutions inside heated machines. The conditions are controlled so that scientists can make sure the crystals grow big and have no cracks.
Zirconia crystals (蘇聯石) are made in laboratory machines. They are far cheaper and sparkle even more than diamonds.
5. Most crystals vibrate an exact number of times each second when electricity passes through them. Quartz watches convert the vibrations of quartz into movement of watch hands.
Crystals can also vibrate in strong light. For example, chromium atoms in ruby crystals produce red light when they vibrate. This can be turned into a thin beam of red light in a laser.
Picture source: https://art21.org/gallery/rackstraw-downes-artwork-survey-1990s/#4
Picture source: https://images.huffingtonpost.com/2014-08-10-RD10173.jpg
