What does crystal come from? How crystals came about

1) Introduce new lessons.

1. Show the crystal necklace and ask: What is it? What material is it made of?

Conversation: Is it made of crystal or glass? What are the similarities and differences between crystal and glass? After learning about "Crystal and Glass" (board book topic), you will find the answer.

2) Learn a new lesson.

1. Get to know quartz.

1) Question: Students, in the last class, we learned about "common rocks", who knows what minerals granite is made of?

5) Summary: Quartz is a colorless, transparent mineral.

2. Characteristics and uses of crystal.

1) Quartz, also known as crystal, buried in the ground in a columnar shape (pointing to the picture). What are the properties and uses of crystals? Please read page 48 of the textbook.

4) Summary: The characteristics and uses of crystals. It is emphasized that Donghai County in Jiangsu Province is a famous "crystal town" in the country, where the crystal quality is excellent, and the output accounts for 80% of the country.

3. Characteristics, uses and production processes of glass.

1) Show the glass and ask: What is this?

Conversation: What material is glass made of? What are its properties and uses? Please continue to read page 49 of the textbook.

5) Summary of teachers and students: With the progress of science and technology, people can also add various substances to the liquid glass to make it a variety of new types of glass to meet the different needs of production and life.

4. Compare the similarities and differences between crystal and glass.

1) Question: What are the similarities and differences between the properties of crystal and glass? Please refer to the illustration on page 50 of the textbook for observation.

4) Combine the similarities and differences in the properties of crystal and glass. (General crystal and glass are colorless, transparent, non-conductive, corrosion-resistant, the difference is that crystal is harder than glass, crystal is a natural material, and glass is a man-made material.) ）

3) Consolidate the summary.

1. Talk: The students have found out the characteristics and similarities and differences between crystal and glass through observation and experiment, and now I invite the students to identify whether the necklace I brought is crystal or glass?

4) After-school extension.

1. Investigate where crystals and glass are used in production and life?

The main component of both crystal and glass is silica.

But the other ingredients are different.

Crystals belong to the trigonal crystal system. The crystals are prismatic with hexagonal cones, the cylindrical surface is striated, and there are often angular bands in amethyst. In nature, crystals are often produced in clusters.

1. Crystal is a rare mineral, a kind of gemstone, quartz crystal, which belongs to the quartz group in mineralogy, and the main chemical component is silica;

2. When pure, it forms colorless and transparent crystals. When it contains trace elements such as aluminum and iron, it is pink, purple, yellow, brown, etc., and is irradiated with trace elements to form different types of color centers to produce different colors, such as purple, yellow, brown, pink, etc. Containing associated inclusions minerals are called inclusion crystals, such as hair crystals, green ghosts, red rabbit fur, etc., and the inner inclusions are rutile, tourmaline, actinolite, mica, chlorite, etc.;

3. Crystals grow mostly in the underground and caves, which need to be rich in groundwater, and the groundwater contains saturated silica, and the pressure in this is about two to three times that of atmospheric pressure, and the temperature needs to be between 550 and 600 degrees Celsius.

Crystal is often translated as quartz, but in fact, the two are the same thing in terms of physical and chemical properties, except that crystal is much purer than ordinary quartz. Basically, the most important component of crystal is silicon dioxide (SiO2), which is the most important mineral that accounts for more than 65% of the earth's crust; The hardness of crystal is between that of glass and diamond. The growth environment of crystals is mostly underground, in caves, which requires abundant groundwater**, groundwater mostly contains saturated silica at the same time, and the pressure needs to be about two to three times the atmospheric pressure.

The temperature needs to be between 550 and 600, and given the right amount of time, the crystal will crystallize into a hexagonal crystal according to the natural laws of the hexagonal system. Normally, in an ideal environment controlled by man, that is, under the condition that the physical and chemical conditions meet the above conditions, the growth rate of crystals is red every day, which is also the standard production rate of many artificial crystals and factories. The resulting crystals, known as "synthetic crystals", are usually cut into chips (chip8) for use in the electronics, computer, and communication industries. It is also called "cultivatedouartz cultured quatrtz", which uses different terms, but actually refers to the same thing.

Generally, the thickness of artificial crystal for industrial use needs to be about 3 cm, that is, 30mm, and it takes about 40 days to grow; For the jewelry industry to grind a crystal ball with a diameter of locm (100 mm) or more, it usually takes about 120 180 days. However, this is the most ideal environment under human control, it is possible to have this speed, in nature, the situation is not so optimistic, because raw materials, water quality, temperature, pressure and other conditions are constantly changing, it is difficult to achieve the ideal situation, usually it takes tens of thousands of times or millions of times to grow into a natural crystal we see today. This is why the "geological age" is often calculated based on "million years", and it is also the reason why "natural crystal" is precious.

When normal crystals are growing, growth lines that are parallel to the axis of the cylindrical tip can be found. Due to the narrow growth space in the underground and caverns, especially when encountering ** or crustal changes, it is even easy to be squeezed by other ores, which often compresses and produces different "crystal planes". In addition, when the crystal is still in a liquid state, it is often coated with other ores and marls to crystallize and grow, such as rutile (later turned into crystals), volcanic marl (later turned into phantom crystals), and so on.

All of this is part of nature and should not be seen as a blemish.