The Natural Process of Decomposed Granite Formation
Decomposed granite (DG) originates from the natural, geological process of weathering. Over long periods, solid granite rock is exposed to elements like wind, rain, and fluctuating temperatures. These environmental factors cause the rock to slowly break down and erode into smaller and smaller pieces. The process is not a sudden, crushing event but a gradual disintegration that results in a unique blend of particle sizes, from large, 3/8-inch pebbles to fine, powdery dust. This variation in particle size is what allows DG to compact into a stable, firm surface, unlike standard gravel, which consists of more uniform, angular pieces. The resulting material is essentially granite in its final stage of natural decay, yet still strong enough for numerous applications. This natural formation process also means that the resulting DG is environmentally friendly, free from chemical processing, and varies in color depending on the mineral content of the source granite.
Core Mineral Components of DG
To understand what DG is made of, one must look at the mineral makeup of its parent rock: granite. The color and final properties of DG are determined by the specific minerals present in the weathered granite. The primary mineral components typically include:
- Feldspar: This is often the most abundant mineral in granite and contributes to a range of colors, including various shades of pink, buff, or white. As feldspar weathers, it becomes a crucial binding agent for the DG particles.
- Quartz: The second most common mineral, quartz is very durable and resistant to weathering. It typically appears as translucent or milky white grains within the DG mixture.
- Mica: These are silicate minerals that flake into small, reflective pieces. Mica adds a sparkling quality to DG, making it visually appealing.
- Other Minerals: Depending on the region, granite can contain other minerals like hornblende, which can give DG a darker, gray or black color.
The mineral composition also explains the wide variety of DG colors available, including gold, brown, red, gray, and black. For example, DG sourced from a quarry rich in reddish feldspar will produce a material with warm, golden or brown tones, while granite with high mica and quartz content might result in a lighter, buff-colored DG.
Types of Decomposed Granite for Landscaping
While the raw material is always weathered granite, DG is often sold in three different types, each with specific properties suitable for various applications. Understanding these differences is key to selecting the right product for your project.
Natural DG (Loose)
This is the most basic and unprocessed form of decomposed granite. It contains no additives or stabilizers and is simply a loose aggregate. It is the most permeable and environmentally friendly option and is often used as a natural, low-cost groundcover or mulch substitute. However, its loose nature makes it susceptible to erosion and tracking into homes, especially in high-traffic or rainy areas.
Stabilized DG
To create a more durable and firm surface, manufacturers mix natural DG with a binding agent, or stabilizer, typically an organic polymer. This mixture is spread and compacted, and when wet, the stabilizer is activated, binding the particles together to create a solid, yet still permeable surface. Stabilized DG is the ideal choice for high-traffic pathways, patios, and driveways where erosion resistance and a firmer footing are necessary.
Resin-Coated DG
For the highest level of durability and stability, DG can be mixed with a resin binder. This creates a hard, durable, and impermeable surface that resembles asphalt but with a more natural aesthetic. Resin-coated DG is best for applications that demand maximum longevity and resistance to erosion, such as driveways with heavy vehicle traffic.
Comparison of Decomposed Granite Types
| Feature | Natural DG | Stabilized DG | Resin-Coated DG |
|---|---|---|---|
| Composition | Weathered granite particles | DG mixed with a binding agent (e.g., polymer) | DG mixed with a resin binder |
| Stability | Loose, prone to shifting and erosion | Very firm and durable once compacted | Highest stability, solid and durable |
| Permeability | Highly permeable | Good permeability | Impermeable or very low permeability |
| Best For | Groundcover, tree rings, garden beds | High-traffic paths, patios, driveways | Driveways, high-wear commercial areas |
| Cost | Least expensive | Moderately expensive | Most expensive |
| Maintenance | Regular raking and replenishment | Low maintenance | Minimal maintenance required |
Applications for Each Type of Decomposed Granite
Decomposed granite's versatility means it has a range of uses in landscaping, with the best application depending on the DG type selected.
- Walkways and Paths: Stabilized DG is the optimal material for creating natural-looking paths. It provides a solid, comfortable walking surface that resists erosion and stays in place better than loose gravel.
- Patios and Outdoor Living Areas: For a rustic yet functional patio, stabilized DG creates a firm, permeable surface that can support outdoor furniture. The wide range of available colors allows for creative design possibilities.
- Driveways: For a durable and visually appealing driveway, resin-coated DG offers the best performance, handling vehicle traffic without rutting or washing out. For a more permeable option, stabilized DG can also work for lighter traffic.
- Garden Beds and Groundcover: Natural, loose DG can be used in place of traditional mulch around plants and trees. It helps suppress weeds, retains moisture, and provides a natural, finished look.
- Xeriscaping: Due to its excellent water retention properties and natural look, DG is a popular choice for xeriscaping, especially in drought-prone areas.
Conclusion
In essence, what is DG made of is a straightforward story of natural geology. It is simply granite that has been broken down by nature over time into a mix of sand-sized particles and small gravel. The variation in its mineral composition dictates its color and characteristics, and through the addition of stabilizers or resin, its physical properties can be enhanced for different landscaping needs. From loose mulch to high-traffic pathways, decomposed granite offers a durable, affordable, and aesthetically versatile option for creating beautiful and functional outdoor spaces. By choosing the right type, you can leverage this natural material to its full potential, ensuring a long-lasting and attractive finish for your project.
