Crystals Facts & Worksheets

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Crystals are solid materials whose components are aligned in a highly microscopic structure to form a crystal lattice that extends in three directions. 

See the fact file below for more information on Crystals, or you can download our 26-page Crystals worksheet pack to utilize within the classroom or home environment.

Key Facts & Information

INTRODUCTION

• Crystal, also known as crystalline solid, is a solid material that consists of atoms, molecules, or ions, that are orderly arranged.
• The lattice formed in crystals extends out in three (3) dimensions.
• Crystals have recognizable structures due to the repeated units formed. Large-sized crystals commonly display flat faces and well-defined angles.
• The word crystal comes from krustallos which is an Ancient Greek word meaning “rock crystal” and “ice”. 

CRYSTALLOGRAPHY

• Crystallography is a branch of science that deals with the study of the atomic arrangement of crystals, along with the geometric structure of crystal lattices.
• One of the techniques in crystallography involves the measurement of the three-dimensional orientations of a crystal’s faces. These measurements can be used to figure out the underlying crystal symmetry. 
• In crystallography, there is a concept called a crystal system. This refers to a set of point groups. A point group, in geometry, refers to a mathematical group of symmetry operations that have a common fixed point. In three-dimensional spaces, there are 32 point groups.
• The corresponding space groups of these point groups are mapped to a lattice system. Crystal systems with similar lattice systems are grouped into a crystal family. 
• There are seven (7) crystal families: (1) triclinic, (2) monoclinic, (3) orthorhombic, (4) tetragonal, (5) trigonal, (6) hexagonal, and (7) cubic. 

• The crystallographic forms of a crystal refer to a set of possible faces it may have related to the symmetries exhibited by the crystal’s components. 

STRUCTURE

• Crystals have regular ordered arrays of components which are held together by uniform intermolecular forces.
• The components of a solid can only be arranged in two (2) different ways: (1) in a way where they form regular repeating three dimensional structures called a crystal lattice which produces crystals and (2) in no particular order or arrangement which produces an amorphous solid.
• Crystals generally have relatively sharp, well-defined melting points since their components are at the same distance from the same number and type of component.
• Crystals are easily recognizable due to their shape and flat faces with sharp angles. However, these physical characteristics do not define a crystal. Not all solids with flat faces and sharp angles are crystals. 
• The scientific definition of crystals pertains to their microscopic atomic arrangement. However, the physical characteristics are often present in crystals. 

FACES AND SHAPES

• There are two (2) types of crystals according to how prominent the flat faces are.
• The first type are called euhedral. Euhedral crystals, also known as idiomorphic or automorphic crystals, refers to crystals that show easily recognizable faces.
• Euhedral crystals have flat faces with sharp angles. These flat faces are also facets, and these facets are oriented in a certain way related to the underlying arrangement of the components of the crystal. 
• Crystals with no obvious faces are the second type, anhedral. 
• Anhedral crystals, also known as xenomorphic or allotriomorphic crystals, refers to crystals with a texture composed of mineral grains and with no well-formed faces. 
• A crystal with some faces is called subhedral.
• The flat faces of a euhedral crystal can be classified as planes of a relatively low Miller index. 
• Miller index refers to a group of three (3) numbers in which these numbers indicate the orientation of a plane in a crystal.

CRYSTALLIZATION

• The process by which a solid (crystal) with a structure composed of highly organized atoms and molecules is formed is called crystallization.
• There are different ways crystallization or the formation of crystals may happen, which include precipitation from a solution, freezing, or deposition directly from a gas. 
• The formation of crystal attributes depends highly on factors such as temperature, air pressure, and/or time of fluid evaporation for liquid crystals. 
• Crystallization has two (2) major steps: (1) nucleation and (2) crystal growth.
• Nucleation is the step related to the appearance of a crystalline phase from either a liquid that is supercooled (with a temperature below the freezing point but still in liquid form) or a solvent that is supersaturated. 
• The second step is crystal growth. This refers to the increase in the size of the particles which leads to their transition to crystal state. In this step, new atoms, ions, or polymer strings are added into the characteristic arrangement of the crystalling lattice.
• There are two (2) types of crystals that can be formed.
• The first type are crystals that are composed of cations (positively charged particles) and anions (negatively charged particles), also known as salt. An example of this type is sodium acetate or the sodium salt of acetic acid.
• The second type are crystals that are composed of uncharged particles, an example of which is menthol. 

MANUAL CRYSTALLIZATION

• Typically, in a laboratory setting, one technique to form a crystal is to dissolve a solid in a solution where it would be partially soluble and at a high temperature to reach supersaturation.
• Once the solid has been completely dissolved, the mixture will then be filtered to remove any insoluble impurities and the filtered mixture will be cooled slowly. 
• The crystals that are formed are then filtered and washed.
• This process is repeated to increase the purity of the crystals formed, and is called recrystallization. 

CRYSTALLOGRAPHIC DEFECTS

• Ideally, all atoms in a crystal must follow a perfect repeating pattern. However, in reality, this idealistic characteristic of crystals is hard
  to achieve because of crystallographic defects or places where the crystal’s pattern is interrupted. 
• One example of a crystallographic defect is a vacancy defect, or an instance where there is an empty space where an atom should be placed.
• Another example is an interstitial defect, or an instance where an atom is squeezed into a place where it does not fit. 
• Another defect concerns impurities. These occur when there is a “wrong” type of atom in a crystal. One good example of this is diamond. A perfect diamond should only contain carbon atoms. However, a realistic diamond crystal might also contain some boron atoms. The existence of boron atoms is an impurity and turns the color of the crystal slightly blue.

COMMON CRYSTALS

• Amethyst is a variety of quartz that is colored purple. It has a trigonal crystal system and belongs to the trapezohedral crystal class. Amethyst is usually used in jewelry and is the traditional birthstone for February. 
• A crystal that consists of strontium sulfate is called celestite or celestine. Celestine has an orthorhombic system and belongs to the dipyramidal class. It is known for its delicate blue color, which is mostly found in sedimentary rocks.
• Malachite is an opaque, green-banded crystal with a monoclinic crystal system and belongs to the prismatic class. 

BENEFITS OF CRYSTALS

• In 1880, a study was done by Pierre and Jacques Curie and they found that changing the temperature of a crystal and then putting pressure on it could create electricity. This electricity is known as the piezoelectric effect, which is commonly used in microphones, quartz watches, and inkjet printers.
• A study was done by CC French regarding the healing effects of crystals. Out of 80 volunteers who were given either real or fake crystals, only six participants said they felt nothing. A psychologist named Richard Wiseman said “it is suggestive that the power of crystals is in the mind instead of in the crystals”, which suggests that the effect of crystals is a placebo effect.

Crystals Worksheets

This is a fantastic bundle that includes everything you need to know about Crystals across 26 in-depth pages. These are ready-to-use worksheets that are perfect for teaching kids about Crystals, which are solid materials that consist of atoms, molecules, or ions, that are orderly arranged.

Complete List of Included Worksheets

Below is a list of all the worksheets included in this document.

1. Crystals Facts
2. I Know
3. One Two
4. Let’s Identify
5. Three Types
6. Pick One
7. Complete!
8. Healing Crystals
9. Common Crystals
10. Which Is Which?
11. My Learning

Frequently Asked Questions

What is the rarest crystal?

Painite is one of the rarest gemstones on Earth. In fact, it is so rare that it has the Guinness World Record for being the rarest. After its discovery in 1951, for many decades there were only two specimens known to exist. By 2004, that number had grown to less than 2 dozen.

What is the heaviest crystal?

The biggest crystal of any type is beryl from Malakialina, Malagasy Republic. It’s 18 m long, 3.5 m in diameter, with a volume of 143 m3, and a mass close to 380,000 kg.

What is the luckiest crystal?

Some crystals are known to bring good luck. Green jade is one of these crystals because it is associated with wealth and fortune. People have believed in the luckiness of green jade for centuries. You often see green jade in places where people do business because it is thought to bring good luck. Red jade is also known to be a lucky crystal, as are citrine and green aventurine.

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Link will appear as Crystals Facts & Worksheets: https://kidskonnect.com - KidsKonnect, September 30, 2022