What is marble? What is its content and hardness?

Marble, also known as marble, has a hardness ranging from 3.5 to 5.5 Mohs hardness.

Marble-Introduction

Marble belongs to limestone and was formed in long-term geological changes.

Marble is named because it is produced in Dali, Yunnan. It includes marble, dolomite marble, serpentine marble, crystalline limestone and dolomite.

Marble is a commodity name, not a petrological definition. Marble is a kind of natural building decorative stone, which generally refers to metamorphic or non-metamorphic carbonate rock with decorative function, and can be processed into building stone or handicraft. It is named after the colorful and ornate stones produced in Diancang Mountain, Dali City, Yunnan Province, China. Marble generally refers to marble, limestone, dolomite, skarn and marble formed by different alteration of carbonate rocks.

Marble is mainly used for processing into various shapes and plates, as the walls, floors, platforms and columns of buildings, and also as the material of memorial buildings such as monuments, towers and statues. Marble can also be carved into handicrafts, stationery, lamps, utensils and other practical works of art.

Marble is soft, beautiful and solemn, elegant in style and diverse in color. It is an ideal material for decorating luxury buildings and a traditional material for artistic carving.

Edit this paragraph back to the catalogue marble-ore raw material characteristics

(1) process classification

Marble is a kind of rock represented by marble, including carbonate rocks and related metamorphic rocks, which is generally softer than granite. Common rocks are marble, limestone, dolomite and skarn. Marble varieties have different naming principles, some are named after the origin and color, such as Dandong Green and Tieling Red. Some are named after patterns and colors, such as Snow White and Ai Yeqing. Some are named after patterns, such as autumn scenery and The Waves. Some are traditional names, such as white marble and crystal jet. Therefore, due to different producing areas, the phenomenon of the same kind of synonyms or different rocks with the same name often occurs.

Marble produced in China can be roughly divided into seven series according to the basic color of polished surface: white, yellow, green, gray, red, brown and black. Each series can be divided into several categories according to the color and pattern characteristics of its polished surface, such as: white marble, rosin yellow, Dandong green, Hangzhou gray and so on. The pattern and crystal size of marble are ever-changing, including landscape type, moire type and pattern type (line pattern, willow pattern, portrait, paleontology and so on. ) and snowflake type. Modern architecture is colorful and constantly changing. Therefore, decorative marble also requires many varieties and colors, which can be used in different parts of the building. Generally, monochromatic marble requires uniform color; Colored marble requires a gradual transition in pattern and depth; Patterned marble requires clear patterns, bright colors and strong regularity. In short, it is best to have beautiful colors, which are convenient for large-scale splicing and decoration, and can be supplied in batches with consistent colors. See table 4.25. 1 for the technical classification of marble in China.

(2) Mineral composition and main characteristics

The mineral composition and characteristics of marble are directly related to the performance and decorative effect of its products. The main mineral compositions and characteristics of several common marbles are listed in Table 4.25.2.

(iii) Chemical composition and physical characteristics

The chemical composition of marble generally does not play a major role in whether it can be used, but it can directly explain the lithology and indirectly affect the physical and chemical properties, which is of certain significance for evaluating the machinability, weather resistance and corrosion resistance of marble. The main chemical components of ordinary marble are shown in Table 4.25.3.

The physical properties of marble are an important index to judge its machinability, and also an important reference for its performance and application scope.

Edit this paragraph back to the table of contents Marble-Marble's purpose.

Marble has beautiful colors and patterns, high compressive strength, good physical and chemical properties, wide distribution of resources and easy processing. With the development of economy, the application scope of marble is expanding and the consumption is increasing, which plays an important role in people's lives. Especially in recent 10 years, with the large-scale exploitation, industrial processing and international trade of marble, a large number of marble decorative boards have entered the architectural decoration industry, not only for luxury public buildings, but also for home decoration. Marble is also widely used to make exquisite utensils, such as furniture, lamps, smoking sets and artistic sculptures. Some marble (including limestone, dolomite, marble, etc. ) can also be used as alkali-resistant materials. Gravel and scraps produced in the process of marble mining and processing are also often used to produce artificial stone, terrazzo, stone rice and stone powder, and can be used as fillers in coatings, plastics, rubber and other industries. Table 4.25.5 lists the main uses of marble.

Edit this paragraph back to the table of contents Marble-Industrial Technical Requirements The industrial technical requirements of natural marble have different emphases for different purposes.

1. Main requirements of natural marble blocks

The main requirements of building materials industry standard (JC202-92) for natural marble blocks are as follows:

The block must have the shape of a right-angled parallelepiped.

The specifications and dimensions of raw materials require a length greater than or equal to 100cm, a width greater than or equal to 50cm and a height greater than or equal to 70cm.

The appearance quality requirements of the same batch of raw materials should be basically the same in hue and pattern; Appearance quality grades such as missing corners, missing edges and cracks. Raw materials shall comply with the provisions in Table 4.25.6.

Physical performance requirements: the bulk density is not less than 2.6g/cm3；; ; The water absorption rate is not more than 0.75%; Dry compressive strength is not less than 20MPa；; The bending strength is not less than 7.0 MPa.

2. Quality requirements of marble for craft carving

It is required that the marble structure is compact, the particles are uniform and not easy to fall off, there are no cracks and inclusions, and the color, pattern, fragmentation and shape meet the molding requirements. The general requirement is greater than 0. 15m3. If it is used outdoors, fresh rock surface is not needed, but it requires good weather resistance and low water absorption.

3. Quality requirements of electrical insulation board

The physical and electrical properties of marble electrical insulation board shall meet the requirements in Table 4.25.7.

Many nonferrous metals, rare metals, precious metals and nonmetallic minerals are all related to marble in origin. It is also an excellent building material and handicraft raw material. Marble has low hardness, which belongs to medium hardness stone and is easy to mine and process. The polished plate presents decorative patterns or color textures, which are very beautiful and can be used as indoor and outdoor decorative materials. Wastes from mining and processing can be made into handicrafts or crushed into terrazzo, terrazzo and other high-quality aggregates, and a few high-density and homogeneous ones can be used for artistic carving and decoration. Because marble is basically composed of pure calcium carbonate or magnesium carbonate, it is extremely sensitive to the dissolution of acid-polluted air. In the urban atmosphere, carbonic acid separated from carbon dioxide and sulfuric acid generated from smoke and dust are always in contact with marble, which affects the supply of marble to varying degrees. In any case, marble is still an ideal material for architectural decoration and sculpture.

Edit this paragraph and go back to the table of contents Marble-Resources. China is extremely rich in marble mineral resources, with large reserves and many varieties, and its total reserves rank among the top in the world. According to incomplete statistics, it is found that there are nearly 400 varieties of marble in China, among which the varieties with different colors are more precious as follows.

● Pure white: Beijing Fangshan white marble; Anhui Huaining, Guichi white marble; Hebei Quyang and Laiyuan white marble; Sichuan Baoxing Shu Baiyu; Jiangsu Ganyu white marble; White marble in Cangshan, Dali, Yunnan; Shandong Pingdu and Ye County Snow White, etc.

● Pure black: Guilin black in Guilin, Guangxi; Black marble in Shaoyang, Hunan; Mo Yu and King Venus in Cangshan, Shandong; Henan Anyang Moyuhei, etc.

● The red ones are: Anhui Lingbi Hongluo; Nanjiang Red in Nanjiang, Sichuan; Laishui red in Laishui, Hebei, and Fuping red in Fuping; Northeast red in Tieling, Liaoning;

● Gray ones are: Hangzhou emblem in Zhejiang; Cloud ash in Dali, Yunnan;

● Yellow ones are: Henan Zhechuan rosin yellow, rosin jade, beige.

● The green ones are: Dandong Green in Dandong, Liaoning; Laiyang green in Laiyang, Shandong, and surf jade in Qixia; Anhui Huaining Bibo, etc.

● Colored flowers include: spring flowers, autumn flowers and ink flowers in Yunnan; Plum blossoms on a snowy night in Quzhou, Zhejiang.

Edit this paragraph to list the evaluation method of marble-good grade: according to the allowable deviation of specifications and dimensions, tolerance of flatness and angle, appearance quality, surface smoothness and other indicators, marble plates are divided into three grades: excellent product, first-class product and qualified product; The grading identification of marble plates is mainly identified by the detection of instruments and measuring tools.

Check the appearance quality: the appearance of different grades of marble plates is different. Because marble is naturally formed, defects are inevitable. At the same time, the advantages and disadvantages of processing equipment and measuring tools are also the reasons for plate defects. Some plates are not full (warped or sunken) and have defects (cracks, sand holes, spots, etc.). ), and the specifications are different (such as lack of edges and corners, wrong plates). According to national standards, all grades of marble plates are allowed to have certain defects, but the superior products are not so obvious.

Choose patterns and colors: Marble plates are rich in colors, diverse in colors and different in patterns, which is the precious charm of marble plates. The basic consistency of color tone, small color difference and beautiful pattern are the concrete manifestations of excellent varieties, otherwise the decorative effect will be seriously affected.

Detection of surface gloss: The surface gloss of marble board will greatly affect the decorative effect. Generally speaking, the polished surface of high-quality marble plate should have a mirror-like luster, which can clearly reflect the scenery. However, due to the different chemical composition of different quality marble, even the products of the same grade will have great differences in gloss. Of course, there will be some differences in the surface gloss of different grades of the same material. In addition, the strength and water absorption of marble slab are also important indexes to evaluate the quality of marble.