About Stone
Granite
“Granite”, is also called “paragnesis”, includes all kinds of igneous rocks which is formed by the cooling down of magma and a type of quartz-porphyry, rhyolite, syenite, pophyry & trachyte of the metamorphic rocks.
Usually, granites that are used for decoration can be classified into “light colours” and “dark colours”. It is based on the colours of the component minerals. For the category of “light colours”, the main minerals are quartz, orthoclase and plagioclase. Only some dark minerals such as biotite and hornblende can be found. We can also find granitoid, granodiorite, quartz-porphyry, rhyolite, syenite, pophyry & trachyte in the category of “light colours”. It can be divided into red, white, gray and multi color spots according to their characteristics of colours.
In the category of “dark colours”, the main minerals are dark and dark-green rhyolite and pyroxene, grayish calcicalse and labradite. It also has some black mica, serpentine and epidote. In this category, it includes basanitoid, gabbro, ultra basaltic and eroded serpentine and epidote. It can also be classified into 3 different range of colours, i.e. black, green and blue.
As granites have many coarse and fine mineral granule, different size of brindle, and different colours, there are lots of varieties can be used for decoration purpose.
Since the silicate and aluminosilicate are the components of granite and they are hard enough, it is resistant to acid, alkaline, erosion and grinding. Also, the well structure of these 2 components contributes the granites to have low absorption and large extent of resistance to stretch, pressure and strength. Therefore , granites are suitable for decorating external walls, floors and stairs. Choosing granite to manufacture large-sized sculpture and artware can also be a good choice.
The resources of granite in China is extremely rich, and many new and grand types of granites are discovered.
“Marble”, is also called “limestone” in petrology. For instance, calcium carbonate is formed by metamorphism and re-crystallization and these processes are affected by the factor of temperature, pressure, hydrotherm. Also, the by-product of some not metamorphosed limestone such as hardened shale, spotted rock cordierite-bearing hornfels will be resulted.
The essential component of marble is calcium carbonate and the main minerals are calcspar and dolomite which are white, milky and gray in colour. Marbles have different colours because some iron, manganese and carbon are subsided with calcspar and dolomite. It is also because there are some greenish minerals such as serpentine, epidote, chlorite, actynolin, mussite, tremolite are found during the process of metamorphism. Thus, marbles have 7 different range of colours, black, red, yellow, green, gray and multi color spots. Moreover, many different veins and structure of marbles result in varieties for decoration.
As the component of marble is calcium carbonate which is slightly acidic and not strength enough, it is not resistant to a cid, alkaline, erosion and grinding. Therefore, it is not suitable for decorating external walls and floors. It is only for indoor wall decoration and making sculpture artware and stairs.
Marbles are distributed in most of the areas in China.