Red lava rock, commonly known as scoria, is a lightweight and porous volcanic material widely used in landscaping and gardening applications. It is valued for its drainage capabilities and vibrant appearance. The red lava rock sold to consumers is available in two distinct forms: a naturally occurring color derived from geological processes and a commercially treated product achieved through artificial coloration. Understanding the origin of the color is key to determining the best use for the material.
The Geological Source of Natural Red Color
The deep color found in natural red lava rock originates from the high concentration of iron within the basaltic magma from which it forms. When this iron-rich magma is ejected during a volcanic eruption, it is exposed to high temperatures and atmospheric oxygen. This exposure causes oxidation, which transforms the iron compounds into ferric iron oxide, or hematite, the mineral responsible for the rock’s reddish hue. Naturally colored scoria is often inconsistent in its shade, displaying dusty, brick-red, or purplish-red tones that vary across a single piece. The degree of coloration depends entirely on the iron content of the lava and the amount of oxygen available during the cooling phase.
Commercial Coloring Processes and Materials
Commercial coloration is applied to lava rock to achieve a consistent, saturated red that natural rock often lacks, meeting consumer demand for uniformity. Manufacturers coat the porous surface of the scoria with specialized, mineral-based pigments to ensure a bright and even color. The primary coloring agent used is typically synthetic iron oxide (hematite), the same chemical compound that causes the natural color. This synthetic pigment is mixed with a durable binder or sealant and applied directly to the rock in a coating process. This treatment allows for the creation of a much brighter, more uniform red than is possible through natural geological weathering.
Practical Differences: Identifying and Using Treated Lava Rock
The most reliable way to differentiate between naturally and commercially colored lava rock is by examining the uniformity. Natural scoria exhibits color variations and inconsistencies, often showing darker or lighter patches, while treated rock displays a deeply saturated and unnaturally uniform color across all pieces. A simple test involves rubbing a piece of the rock with a damp, white cloth; if significant red pigment transfers, the rock has been commercially colored. Consumers should note that dyed lava rock is susceptible to fading over time, particularly when exposed to direct sunlight and UV radiation. For use in sensitive environments like aquariums or planting beds, it is important to confirm the specific pigment and binder used are inert and non-toxic, as some coatings may leach substances into the water or soil.