Volcanic rock comes in a wide variety of colors and textures depending on its mineral composition and how it was formed. The specific hex color for volcanic rock can vary greatly, but there are some common shades that are often associated with these igneous rocks.
What is Volcanic Rock?
Volcanic rock is formed from magma or lava that has cooled and solidified. When magma erupts from a volcano onto the surface as lava and cools rapidly, dense volcanic rocks such as basalt can form. Slower cooling allows large mineral crystals to grow, forming rocks like granite. Volcanic rocks can range from light to dark and fine-grained to coarse-grained.
Some of the most common types of volcanic rocks include:
- Basalt – Fine-grained, dense, dark gray to black
- Andesite – Intermediate color, not as dark as basalt
- Rhyolite – Light colored with visible crystals, a felsic rock
- Pumice – Very porous and lightweight volcanic glass
- Obsidian – Dark volcanic glass
The specific appearance and mineralogy of a volcanic rock depends on the lava composition, eruption environment, and cooling history. But overall, these rocks tend to reflect the common gray, brown, red, and black hues found in volcanic regions.
Common Volcanic Rock Colors
Here are some of the most prevalent colors associated with volcanic rocks and their hexadecimal (hex) color codes:
| Volcanic Rock Color | Hex Code |
|---|---|
| Dark gray to black | #333333, #222222, #000000 |
| Medium to dark gray | #666666, #555555 |
| Brownish gray | #8B7355, #5F4C3B |
| Dark red | #8B0000 |
| Dark reddish brown | #5F3D2E |
As you can see, darker muted colors tend to predominate. Very dark gray or black basalts and obsidians are quite common volcanic rocks. Brownish-reds and reddish-browns are also prevalent in many lava flows and volcanic regions.
Key Factors Affecting Volcanic Rock Color
There are several factors that influence the specific colors of volcanic rocks:
- Mineral content – Mafic lava with high iron and magnesium content tends to produce darker basalts and gabbros. Felsic lava with higher silica results in lighter rhyolites and granites.
- Crystal size – Fine-grained volcanic rocks appear darker than coarse-grained equivalents.
- Cooling rate – Faster cooling produces finer crystals and darker rocks.
- Oxidation – Exposure to oxygen can produce more reddish or brownish minerals like hematite and limonite.
- Impurities – Trace minerals and elements can tint the rock.
- Weathering – Age and exposure to water/air alters surface colors over time.
Understanding these influences can help explain the diverse palette of volcanic rocks in nature. For example, a rapidly cooled mafic lava flow would produce a dark fine-grained basalt, while viscous felsic magma cooling underground results in light-colored granite with large crystals.
Typical Hex Colors for Common Volcanic Rock Types
Here are some volcanic rocks with typical hex color values:
Basalt
| Color | Hex Code |
| Dark gray to black | #1F1209, #423325, #432C20 |
Basalt is a mafic volcanic rock that forms dark gray to black smooth, fine-grained lava flows. Abundant dark iron and magnesium-rich minerals like pyroxene give basalt its dark color.
Andesite
| Color | Hex Code |
| Medium to dark gray | #6D6763, #4B4742 |
| Brownish gray | #897F72 |
Andesite is an intermediate volcanic rock with a speckled appearance due to visible mineral crystals in a dark gray to brownish matrix. The minerals reflect its composition between basalt and rhyolite.
Rhyolite
| Color | Hex Code |
| Light gray to tan | #DDD6D3, #C5B8AE |
| Reddish brown | #B06548 |
Rhyolite is a felsic volcanic rock often displaying beautiful banding patterns in shades of gray, white, pink and red. The high silica content produces light colors with flow banding caused by mineral crystallization.
Obsidian
| Color | Hex Code |
| Black | #171913, #0C0A08 |
| Dark brown | #3B362C |
| Dark green | #0F3B17 |
Obsidian is a natural volcanic glass, usually black, brown or dark green. Its dark colors come from iron and magnesium-rich mafic lava cooling too quickly for crystal growth. Green and brown specimens reflect trace minerals.
Pumice
| Color | Hex Code |
| Light gray | #DBD7D2 |
| Pale Yellowish | #EBE3DE |
Pumice is a porous, frothy volcanic glass formed during explosive eruptions. It is typically light in color ranging from white, gray, yellowish to pale brown due to abundant gas bubbles and high silica composition.
Weathering Effects on Volcanic Rock Color
Volcanic rock colors can change over time as they are exposed to weathering at the earth’s surface. Some effects of weathering include:
- Oxidation – Converts dark minerals to redder, brownish hues
- Hydration – Produces clay minerals, altering rock color
- Lichen/moss growth – Can cover rocks with grayish-green tone
- Bleaching – Extended sun exposure lightens darker minerals
- Staining – Iron oxidizes to form orange-brown stains
For example, a fresh basalt lava flow may start out very dark gray. Over years of exposure, the iron oxidizes to form a rusty reddish-brown weathered basalt. Weathering also breaks down minerals to clays, lightening the tone.
Using Volcanic Rock Colors in Design
The natural colors of volcanic rocks can provide inspiration and attractive shades for graphic, web, interior, and product design. Some ideas include:
- Use black, gray, or brown hues paired with reds and oranges for a bold, earthy palette.
- Incorporate volcanic rock textures and visuals – can evoke a primal, organic feel.
- Reflect the muted tones found in nature – avoid bright, saturated colors.
- Consider integrating volcanic glass shapes and forms – ellipses, fluid lines.
- Pair volcanic colors with natural materials like wood, fiber, wool.
When selecting a specific hex color for volcanic rock, consider the type of rock and whether it is meant to appear fresh or weathered. A smooth obsidian surface could be #171913 while a weathered basalt might use #5F3D2E. Keep in mind the range of grays, browns, reds and blacks found in volcanic regions.
Conclusion
Volcanic rocks exhibit a wide spectrum of colors depending on factors like composition, crystal structure, and exposure to weathering. While they can range from light tan rhyolites to glassy black obsidian, volcanic rocks tend to be associated with darker grays, browns, and reds. Common hex color codes include shades of black, dark brown, dark red, medium gray, and brownish-gray. When selecting a specific hex value, consider the volcanic rock type and its typical mineral characteristics and textures. The natural yet intense hues of volcanic rocks can provide an inspiring palette for designs seeking an earthy, primal feel.