Marble vs Onyx: What Are They, And What’s The Difference?

The marble vs onyx debate is an argument that has been going on for centuries.

Both rocks look similar but have different characteristics.

Let’s look at what each stone is and what its differences are.

Marble vs Onyx: The Facts

What Is Marble?

Marble is a sedimentary rock formed by weight and pressure over long periods.

Marble usually consists of either calcite or dolomite, and it occurs in many colors, including white, black, yellow-gray, grayish-brown, greenish-blue, to bluish violet.

It’s often used in construction and art pieces.

The Physical Properties of Marble

Marble has been known to have different colors depending on the conditions in which it was formed.

Still, these color variations are typically not considered when used as an architectural stone.

The stone’s overall appearance can classify the marble and its origination based on how pure or impure the marble’s mineral content is.

Marble sometimes contains fossils that were once locked within sedimentary rocks tens of millions of years ago.

Marble’s crystalline structure means that it has good resistance to both weathering and frost.

The stone is often cool to the touch. It’s also interesting that marble will neutralize many different types of acids on contact.

What Is Onyx?

Onyx is a metamorphic rock formed when bands of parallel quartz crystals were laid down at high temperatures, usually created in gas pockets from lava flows.

Onyx has stripes and predictable wavy lines found in most of it, ranging from brown, red, and orange to white.

Black onyx in its original form is rare, and is often confused with black tourmaline.

Most of the black onyx found on the market today has been dyed to appear this way.

Sometimes onyx has no stripes at all, which is where white onyx gets its name. 

The Physical Properties of Onyx

Onyx is primarily known for its hardness and the fact that it’s scratch-resistant.

It’s a variety of quartz, so it is composed mainly of silicon dioxide molecules.

The stone accepts dye of any color.

Because of this versatility, it is often used in art and jewelry making throughout history.

There are many different types of onyx available today because each different composition comes with varying physical properties.

For example, black onyx contains iron oxide, while white onyx contains titanium or zirconium silicate.

This ingredient variance makes black onyx much softer than its counterpart, making them both desirable depending upon what you need your stone for.

Regardless, all types of onyx will resist scratches from everyday wear and maintain their clarity over time.

Marble vs Onyx: The Similarities

Marble and onyx do share some similarities.

Marble displays the same mineral composition as onyx; both are composed of quartz and various mica minerals such as muscovite, sericite, or phlogopite.

Both stones have patterns in the rocks with similar colors, depending on the type.

Marble vs Onyx: The Differences

Marble and onyx are remarkably similar, but they have some noticeable differences.

Marble is a metamorphic rock, while onyx is a form of chalcedony quartzite.

Marble often looks like it’s made up of many smaller stones, while the surface of onyx can be dotted with white lines or inclusions.

However, the most significant difference between these two stones is their color patterns: marble patterns show in veins and swirls, while the stripes in onyx are usually straight or wavy but not vein-like.

Marble needs to be polished to obtain its mirror-like polish.

Onyx shines on its own without manufactured polishing.

Marble vs Onyx: Why the Two are Confused

Certain of the stone’s similarities often confuse the untrained eye.

  • Both stones have smooth, hard surfaces once they’ve been cut and polished.
  • Both stones can appear in different color variations, including greys, whites, and black. Both may or may not have lines in them, depending on the kind.
  • Both kinds are used in construction in the modern day.

How to Identify Marble

The easiest way to identify marble is by its polished and veined appearance.

The veins can be white, black, or deep brown, solid blue lines of color that are often found in a swirl pattern on the surface.

Polished surfaces have an almost glassy sheen and reflect light like a mirror when exposed to direct sunlight.

When you find marbles with these markings, it’s essential to know they’re likely Italian, because this is what many countries use as their standard for marble identification.

The fastest way to tell if your material is marble is by running your fingers over the surface to feel for any irregularities from veins or other imperfections.

Its weight and texture can also identify marble.

Many people use this as their primary method for identifying the stone because it has become such an iconic symbol. 

Feel along the surface with your fingers to assess how thick and heavy each slab is before deciding on whether they’re marbled slabs.

If the slabs are exceptionally light and feel like they will break with pressure, it is more than likely not marble.

If the piece has an identifiable heaviness to it that makes you shudder when you touch it, there’s a good chance this is what you’re looking for.

How to Identify Onyx

While it may not be the most common stone, onyx is relatively easy to identify.

What makes onyx so easy to spot is its colors. It’s found in black, white, and striped versions.

Onyx stones can also have a hint of orange or red, but this happens mostly with banded varieties.

When looking for an onyx gemstone on a piece of jewelry, pay attention to those colors near your eye level from about three feet away.

If you see something that meets these criteria, then congratulations, you’ve most likely found yourself some onyx.

The identifying features of onyx include dark brown stripes alternating with light-colored bands, which resemble the teeth within a human mouth when they grind together.

Alternatively, the stone can be identified by patterns such as wavy lines (called adularia), zigzags, and herringbone.

They usually don’t look like veins. 

Where to Find Marble

The best places to find marble in the United States are on either side of the Great Lakes.

Marble is quarried from large deposits found there, and quarrying is widespread in both Minnesota and Wisconsin.

In addition to this area, you can also find quality marble in locations like India, Brazil, Italy, Greece, and China.

Where to Find Onyx

Onyx is found worldwide, but it can be challenging to spot in the wild, so to speak, simply because its darker shades blend in so well with the surrounding rocks.

The easiest way to find it for jewelry or construction is by finding a manufacturer or supplier online. 

What Marble is Used For

Marble was historically used for columns, floors, and staircases because it could be cut into shapes desired by architects or builders.

As long as man strives to build and carve, builders and artisans choose marble as a solid and reliable building material.

It’s considered durable and versatile.

Because the color variation is so vast, marble finds its way into constructive pieces.  

  • Tabletops
  • Countertops
  • Flooring
  • Foundations
  • Staircases
  • Wallcoverings

Regularly, you’ll find marble carvings and full-fledged sculptures on church altars.

Builders often choose the stone as the base for statues and buildings, such as castles, for decorative purposes.

What Onyx is Used For

Egyptians used onyx for jewelry because it’s so hard.

Today, that tradition continues as the stone is scratch-resistant.

Sometimes, it’s still used as countertops in construction.

In addition to being worn as jewelry pieces like rings and bracelets, onyx has been known since antiquity for use in carvings and small sculptures due to its durability under high-pressure conditions from grinding by hand tools and other abrasives.

Both marble and onyx are beautiful stones with many practical purposes.