Crystallography

Crystallography is the study of atom arrangements in crystals. It use X-ray diffraction and other techniques to analyze its structures, properties, and molecular arrangements. This field is important in chemistry, physics, and biology, contributing knowledge for understanding the principles of the physical world.

Diffraction: Process of light bending around an obstacle.

The word "crystal" from the Greek word krystallos, meaning "icy cold".

These crystals have formed from hot water solutions within Earth.

History

[Q1] It's said, back then, that crystals and colorless quartz were ice that froze so hard it couldn't melt.

inogarnic: Not made of living material, or (of chemical substances) containing no carbon or only small amounts of carbon: Salt is an inorganic chemical.

The Crystal Palace was built for the Great Exhibition of London (1851), then destroyed by fire (1936). Roof and outer walls were made of ~300,000 glass panes, not crystals.

Most gemstones are natural crystals used for beauty, durability, and rarity. , mostly cut and polished.

With properties as natural minerals, these re grown naturally and cut as gemstones.

Fake Crystal

Some objects called "crystals" are glass and not truly crystalline. Glass has little structure, as it is cooled too quickly for the atoms to arrange themselves into regular order, and is said to be amorphous.

Crystal Lining

Lines resembling plants are crystalline growths - a crucial process that consists of the addition of atoms and ions.

Crystals form the Earth, moon, and meteorites. Out of many elements, natural crystallines are mostly made of oxygen, silicon, and a few metals, like iron and calcium. Crystalline particles wake up in mountains and form ocean floors. When we cross the beach, we tread on crystals and use them at work and home. They’re vital to modern technology.

tread: To step/walk on.

Earth is made of three layers: the crust, mantle, and core, mainly made of solid minerals. Some like pure marble and quartzite, are made of one mineral, but most are made of two or more.

Granite is the most common rock of the Earth’s outermost layer. It consists mainly of quartz, biotite, and mica.

Organic Crystals

Crystals don’t only grow in rocks. The elements making up most rock-forming minerals are also important to life on Earth, like calcium and apatites in bones and teeths.

Tiny apatites make up the skeleton of vertebrate animals (with backbones) like humans and horses.

Gallstones are sometimes formed inside an animal's gall bladder. A cow's is made of the same crystalline composition.

Natural Beauty

Well-formed crystals are objects of extreme value. Conditions have to be right for crystals to grow and any later changes must act to protect rather than destroy.

Even if some survive, many are destroyed by miners and workers. The crystals shown are roughly 60% of their real size.

Topaz are gemstones of the silicate mineral family. Most are yellow, brown, and blue. Blue colors are often adjusted by irradiation and heat. It's the birthstone of November and is symbolized as love and good fortune.

Proustites are cherry red-colored crystals known as ruby silvers and are often found along with silver deposits.

Calcites are one of the most common that occur as crystals in many shapes and colors. This image consists of typical fine colorless slightly red crystals.

Crystals on the outside...

Well-formed crystals have some symmetrical traits, like faces, and parallel edges, and parallel faces on opposite sides. Crystals may have three types of symmetry. If it can be divided into two, so that each half is a mirror image of the other, the line dividing them is called the “plane of symmetry.”

If it's rotated around imaginary straight lines and face patterns appear many times in a turn, then the lines are “axis of symmetries”.

How many times patterns appear around an axis determines whether it's twofold, threefold, fourfold, or sixfold.

Seven Crystal Systems

Crystals are placed in one of the seven major categories called Seven Crystal Systems. Cubic system crystals have the highest symmetry. Most symmetricals have 9 planes, 12 axes, and a center of symmetry. Triclinic system crystals have the least symmetry with only one or no symmetry center.

Crystal on the inside...

The Internal Atomic Structure of crystals determines their regular shape and other properties. Each atom has its position and is tied to others. Atoms of some minerals always group in the same way to form crystals of that mineral. In 1808, English chemist J. Dalton defined his theory that matter is built up from tiny particles called atoms. A century later, Max Lon Laue found that X-rays could determine the arrangements of atoms in solids.

Physicist Max Von Laue (1879-1960) showed with an X-ray photograph that crystals were possibly made of atom planes.

Not Carbon Copies: Diamonds and graphites are formed from carbon, but have many differences in properties, which is explained by external structures.

Graphite have carbon atoms linked in a hexagonal (six-sided) arrangement in widely spaced layers.

Its layers are weakly bonded and can slip only weakly bonded and can slip easily over one another, making graphite one of the softest minerals.

Actinolites are silicate minerals with basic units of tetrahedron (four faces) of a silicon and four oxygen atoms (SiO4). Actinolites have structure based on double chains on these tetrahedra.

Diamond: In a diamond, each carbon atom is strongly bonded to four others to form rigid compact structure. This structure makes diamonds much harder than graphite.

Cleavage

Some crystals split along well-defined planes called cleavage planes which are characteristic s for all specimens of that species. Cleavage forms along the weakest plane in the structure and is direct evidence of the orderly arrangement of atoms.

Crystal Colors

Color can be crystals' prominent features. The causes are vast and some are mostly from our eyes and brains reacting to different light wavelengths. When daylight falls on them, some wavelengths may be reflected and absorbed.

Idiochromatic

Some minerals are nearly always the same color because certain light-absorbing atoms are an essential part of their crystal structure. These minerals are described as idiochromatic. For example, copper minerals are nearly always red, green, or blue according to the nature of the copper present.

Sulfurs are idiochromatic minerals that are mostly bright yellow and are often found in masses around volcanoes.

Isaac Newton: Newton was known for his work on the nature of light. He found that white light is split into seven different colors.

Azurite: Always a blue-colored copper - hence the term azure blue.It was crushed and used as a pigment in ancient times.

Allochromatic: Many minerals occur in many colors caused by impurities or light-absorbing defects in the atomic structure, such as quartz, diamond, and berylm can be red, green, yellow, and blue. These minerals are described as allochromatic.

Rhodochrosite: Manganese minerals such as rhodochrosite are usually pink or red. The bright red color of some beryls is due to a tiny amount of manganese.

Fluorite: When exposed to invisible ultraviolet light, some minerals emit visible light of various colors. This is called fluorescence usually caused by foreign atoms called activators in teh crystal structure. The fluorescent color oif a mineral is usually different from its color in daylight. This fluorite crystals is green in daylight.

Identification

“What is it?” is first asked about a mineral, crystal, or gemstone. To identify a crystal, it’s needed to test its properties. Most minerals have fixed chemical compositions and an identifiable crystal structure. These give, habit, cleavage, and surface features are studied using hand lenses, but this is mostly not enough for identification.

Absorbed in Stone

A spectroscope is often used to distinguish between gemstones of a similar color. Light engters throught a slit of similar color. Light enters through a slit and separate into its spectrum of colors. If a gemstone is put between the light source an the slit, dark bands appear in the spectrum, where wavelengths have been absorbed by the stone.

Seeing double: An important property of some crystals is birefringence, or double refraction. Light traveling through the calcite is split into two rays, causing a doubled image.

Natural Growth

Crystals grow as atoms arrange layer by layer. They can form from gas, liquids, or solids and mostly start growing from the center of the surface. Growth continues by the addition of similar material to the router surface until the supply stops. It’s rare to find a perfect crystal. Temperature, chemical conditions, and how big the space all affect growth. It’s said that in an hour, millions of atoms are arranged layer by layer.

Twisted: Crystals can be bent or twisted. This may be due to being bent by outside force during growth.

In the pocket: Holes in rocks often provide space in which crystals can grow. Cavities containing fine gem-quality crystals are known as gem pockets
Taking shape: Many minerals crystallize from watery solutions. We only see the final product but can often work out a sequence of events, like this fuorite crystal on the right.
Changed by force: Due to high temperatures, minerals in solid rock can recrystallize. This process is called metamorphism. The blue kyanite and brown staurolite crystals in this specimen have been formed in this way.

Hexagonal-Shaped Rocks

The Giant’s Causway near portush in Count Antrim, Northern Ireland, lookl like a collection of hexagonal crystals. But, the phenomenon is not crystal growth but joining due to contraction as the basltic lava cooled.

Dentritic is the term used to describe the habit of these crystals that are tree-like.

Pisolitic/Pisolite: Sedimentary rock texture characterized by pea-sized dots called pisoids, which are mostly made of calcium carbonate or other minerals. "Pisolite" is from the Latin word "pisum," meaning "pea".

Growing from Seed

Experts have tried to make natural crystals artificially for over a century. In recent times a range of artificial crystals has become important to modern technology. The need for a huge amount of perfect crystals has led to more and more synthetic crystals being made, and it could be said that future development in electronics will depend on the development of crystal-growing techniques.

1: Liquid cools swiftly. 2: Crystal grows slowly, becoming clear.

3: At room temperature, grows slowly due to evaporation.

4: Cooling stops, but evaporation continues. It stops growing

Melt Technique

Excellent crystals may be grown by evaporation of a supersaturated solution no more will dissolve) of a salt such as halite, alum, or ammonium dihydrogen phosphate (ADP). In the experiment show, piowedered ADP containing a smlal chrome0alum impurity has been completely dissolved in boiling water and then cooled.

Crystals at work

Basic crystal understandings are made prior 20th century, it's recently crystal tech became crucial.

Now, control circuits, machines, electronics, medicine, industrial tools, and communications, and even shopping objects, like credit cards, use crystals.

Crystal labs make silicon chips, ruby laser rods, and many forms of diamonds for tools.

Quartz

Quartz is Silicon dioxide. It occurs as individual crystals and fine-graned masses in a large variety of forms, patterns, and colors. If conditions are right, giant crystals can grow (Brazil is famous for these). Biggest known crystals was about 20ft (6 cm) long and weight more than 48 tons/44,000 kg.

Amethyst: The most costly quartz. It can be found in the Ural mountains, Brazil, Uruguay.
Sands and Gems: As quartz is relatively common and hard, it forms the major part of sand and dust in the air. Any contact with sand can damage gemstones, mainly softer ones.
Agate: The quartz grains in chalcedony are arranged in layers and their buildup is clearly visible in the different colored layers of agate.
Tiger's-eye: The structure of the tiny fibers of asbestos was exactly reproduced by the quartz, and this gives rise to the light reflection or the "cat's-eye".

Named as a tiger's-eye due to looking like the animal's eye.

Diamond

Diamond comes from the Greek word "adamas", meaning "unconquerable", given to the stone due to its supreme hardness. Diamond is made of pure carbon and has a very strong structure, making it harder of al minerals. Studies show that diamonds are formed 200 km within Earth. First found 2,00 years ago. Today over 20 countries (mainly Australia) make diamonds.

Uncouquerable Belief

Napoleon Bonaparte is said to be the first Consul to wear a sword set with the Regent Diamond. He hoped the crystal would bring him victory in battle. An ancient belief said that a diamond made its wearer unconquerable.

Regent Diamond used to be the outstanding gem of the French crown jewels; it was discovered in India in 1701 and weighed 410 carats in rough form. It's worth $60 million.

Corundum

Ruby and sapphire of the mineral corundum, an aluminum. Only true red stones are called rubies and the blue are sapphire. Other colors are yellow or pink sapphire.

Peacock Throne: Shah Jahan, ruler of Persia in 1627, was famous for his knowledge in gems. His famous Peacock Throne was set with hundreds of gems including 108 rubies.

Star ruby: Some rubies display stars caused by fine needle-like inclusions, like the Rosser Reeves.

Star-sapphire were believed to be evil. Each three lines meant faith, hope, and destiny.

Opal

The popularity of of these flashy stones has risen and fallen over centuries. Romans used it as a power symbol but eventually deemed as unlucky.

This piece of white opal comes from Czechoslovakia, the source used by the Romans. This region was once part of Hungary, and the opal from here is usually described as Hungarian.

Opals without flashes of color are called potch opal.

References

Sources of this page: Crystals and Gem - DK Edition

Quizzes

[Q1] Quiz 1
[Q2] Quiz 2

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