Rocks are popular materials in landscapes. A visit to many residential and commercial buildings will reveal the presence of rocks as mulch, edging, decorative stepping path stones or focal point boulders. Many varieties of rock types are strong, durable and attractive in a landscape.
Granite is a common igneous rock that forms below ground from volcanic magma. This slow-cooled rock contains quartz, feldspar, mica and often hornblende minerals. Granite has large grains that are easy to see and may be a variety of colors based upon the chemical composition of the magma. These rocks are one of most popular types of building materials for both indoor and outdoor use. In the garden, you can find granite mulch, boulders, edging blocks and stepping stones. Due to its color variations and interesting mineral sizes and shapes, granite is complimentary to most homes and gardens.
Basalt is an igneous rock that forms on the outside of the volcano from lava flows and is the most common rock in the Earth's crust. Olivine, pyroxene and plagioclase are typical mineral components of basalt; however, due to its quick cooling, the mineral crystals are not visible with the naked eye. Basalt rock mulch is very common and sometimes has an interesting texture with small holes in the rock. The holes form as gases escape from the lava as it cools. Basalt boulders make good focal points in a garden.
Scoria is an igneous rock that forms from a violent volcanic eruption. When the lava erupts from the volcano, gases escape, creating holes in the scoria when it cools. Scoria is one of the most common rock mulches due to its distinctive texture, its hardness and its deep reddish brown color once oxidized. Many mulch suppliers call scoria "lava rock."
Slate is a metamorphic rock that forms from shale under very high temperature and pressure. The rock will break along parallel fractures close together in the rock. This fracturing allows the slate to break into sheets. Use slate sheets as stepping stones in a garden or along the edges of landscape beds.
Pumice is an igneous rock that also forms from a violent volcanic eruption. Froth forms as gases from the lava expand and cause the foam on top of the cooling lava. The pumice quickly cools, trapping gas bubbles in the rock. Pumice can form from lavas with different mineral contents, which slightly changes its coloring. Pumice is popular landscape mulch because of its texture and variety of colors.
Sandstone is a sedimentary rock that forms from quartz sand grains. The sand grains cement together from compaction or the presence of quartz or calcite acting like glue. Sandstone mulch, edging, boulders and bricks are popular in landscapes. Sandstone comes in many colors and may have layered patterns that add interest to the surroundings.
Limestone is a sedimentary rock that forms from the precipitation of calcium carbonate. Most limestone forms in quiet settings and forms layer deposits. Limestone is popular as mulch, edging and brick pavers. Gardens with acid-loving plants should not use limestone as it may raise the pH of the soil.
- Photo Credit garden rock border image by Jim Mills from Fotolia.com
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