The use of stone in garden landscapes has a long history. Natural stone is an ancient building material with high strength, good decoration, high durability, and a wide range of sources. The advancement of modern mining and processing technology has led to the widespread application of stone in modern landscapes. Whether it is the stone steps in Roman courtyards or the stone squares in modern gardens, whether it is the rockery, revetment in classical gardens in the East, or the placement of stones in Japanese courtyards, stone, as an ancient building material, has always held a place in the history of human gardens and has become more vibrant through the advancement of processing technology.
1、 Classification of stone materials
1. Stone: Refers to the general term for materials extracted from natural rock masses of sedimentary, magmatic, and metamorphic rocks, processed and shaped into plate-like and columnar materials. Stone is a material with dual functions of architecture and decoration; Natural decorative stone generally refers to marble, granite, and some slate used for building decoration, mainly referring to its mirror-faced board, as well as fire-fired board, matte board, sandblasting board, and block stone, strip stone, and board used for decoration. The classification method of stone is not unified, and according to the process and commerce, it is classified into marble, granite, and slate.
(1) Marble: Various types of carbonate or magnesian carbonate rocks with decorative, blocky, and processable properties, as well as related metamorphic rocks, collectively referred to as marble; The main rock-forming mineral is calcite or dolomite, and its chemical composition is carbonate rock (calcium carbonate, magnesium carbonate).
Pure marble is white (often called White Marble in China), marble often contains other impurities, carbon is black, iron oxide is rose color, orange-red, iron oxide, copper is green, so marble presents white, black, red, yellow, dark green, gray, brown and other colors; Due to the main chemical components of marble being CaO and MgO, it has poor acid and alkali resistance and is generally not used for outdoor decorative panels.
(2) Granite: Various types of magmatic rocks with decorative, blocky, and processable properties, as well as metamorphic rocks mainly composed of silicate minerals, are collectively referred to as granite; Granite is the strongest, most stable, and most colorful rock among magmatic rocks, and its performance is superior to marble and other rocks; Its bulk density is 2.63-2.8g/cm3, and its compressive strength is 100-300Mpa.
Granite is a fully crystalline rock composed of quartz, feldspar, and a small amount of mica and dark minerals. It has good durability and strong frost resistance and has a service life of 75-200 years. According to the degree of surface processing, it is divided into the fine-faced board (RB), which has a flat and smooth surface, mirror-faced board (PL), mirror-faced board (PL), and rough-faced board (RU) with a rough and smooth surface.
(3) Slate: With a plate-like structure, it can be peeled into pieces along the bedding plane and used as decorative materials. Shallow metamorphic rocks formed through slight metamorphism are collectively referred to as slate.
2、 The physical and chemical characteristics of stone materials
1. The color and texture of stone are closely related to the mineral composition they contain. The color of granite mainly depends on the color and quantity of feldspar. Different varieties of feldspar present different colors. Potassium feldspar is flesh red and gray-white, so when the rock contains more potassium feldspar, it often turns red, such as “Maple Leaf Red” in Guangxi, “Guifei Red” in Shanxi, and “Indian Red” in India. It should be noted that many red granites containing potassium feldspar will gradually fade under sunlight or even at higher temperatures.