The Ultimate Guide to Cutting and Trimming Onyx Countertops

cutting onyx countertop

Onyx, a naturally translucent material renowned for its beauty and elegance, has become a popular choice for countertops in homes and businesses.

Its unique pattern variations and color depth create a stunning visual appeal that is unmatched by other materials. However, the exquisite nature of onyx makes it imperative to cut and trim it properly to maintain its integrity and aesthetic.

It’s not simply about getting the dimensions right; it’s also about ensuring the material does not chip or crack in the process. But before we delve into the intricacies of cutting and trimming this beautiful stone, let’s not forget safety.

Working with stone requires the utmost care and appropriate safety precautions to prevent accidents.

So, whether you’re a seasoned contractor or a DIY enthusiast, this guide is designed to provide you with the necessary knowledge and techniques to work with onyx countertops safely and effectively.

Tools and Materials

List of Essential Tools and Materials

In my experience working with Onyx, I’ve learned that having the right tools makes all the difference. Here’s a list of the essential tools and materials you’ll need:

  1. Diamond Blade Saw: This is the go-to tool for cutting onyx. Its razor-sharp diamond edge makes precise cuts without causing chips or cracks.
  2. Polishing Pads: After cutting, you’ll need to smooth out the edges to give your countertop that sleek, finished look.
  3. Clamps: These will hold the onyx slab in place while you’re cutting. You don’t want any movement interrupting your work.
  4. Straight Edge: This will guide your cuts to ensure they’re straight and even.
  5. Tape Measure: Precision is key when working with onyx.

Importance of High-Quality Tools

I can’t emphasize this enough: invest in high-quality tools. I remember cutting my first onyx slab with an old, cheap saw. It was a disaster.

The blade became blunt mid-cut, leading to a rough, uneven edge that took ages to smooth out. Spending a bit more on quality tools isn’t just a good investment—it’s a necessity.

Safety Gear

Safety is paramount. The first time I cut onyx, I thought my regular glasses would suffice as safety goggles.

A speck of onyx dust quickly proved me wrong, catching in my eye and causing quite a bit of discomfort. Here’s what you’ll need for safety:

  1. Safety Goggles: These will protect your eyes from dust and debris.
  2. Dust Mask: Onyx dust isn’t something you want to breathe in.
  3. Ear Protection: The saw can get quite loud, so protect your hearing.
  4. Heavy Duty Gloves: These will protect your hands from any sharp edges on the onyx slab.

Remember, the goal is to create a beautiful countertop, not to win a trip to the emergency room. So, gear up and stay safe!

Preparing for the Project

Before you start cutting into that gorgeous slab of onyx, there’s some preparation to do. Preparing in advance will set you up for success and make the whole project a lot smoother.

Measuring and Marking the Countertop

Just like a chef needs to prep before cooking, you need to measure and mark your countertop before cutting.

This part always reminds me of my school days, when my geometry teacher would say, “Measure twice, cut once.” Well, he was right.

Get your tape measure and straight edge, and double-check those measurements before making any marks. Once that’s done, use a non-permanent marker to outline where you’ll cut.

The feeling of drawing that first line is always a bit nerve-racking, but it signifies the beginning of something great.

Gathering Necessary Information

This part is all about doing your homework. I remember working on a project where I just jumped in without understanding the specific properties of the onyx I was working with.

Big mistake. The project took twice as long as it should have, and I ended up having to buy more material due to my own errors.

So, do your research. Learn about the specific type of onyx you’re working with, its density, its strength, and any peculiarities it might have. Information is power, my friends.

Creating a Detailed Plan

Planning goes hand-in-hand with gathering information. Based on what you’ve learned about your material, sketch out a detailed plan of what you’re going to do and how you’re going to do it.

This will be your roadmap. I always get a bit excited at this point – it’s like plotting a journey. Knowing where you’re going makes the whole process so much smoother and more enjoyable. So take a deep breath, plot your course, and get ready to create something beautiful.

Choosing the Right Cutting Method

Selecting the appropriate cutting method is an essential aspect of any countertop fabrication project. There are a few options available, each associated with its own strengths and weaknesses. Let’s dive into them:

Cutting Methods

1. Wet Saw

Trust me when I say this, a wet saw is a countertop fabricator’s best friend. Nothing beats the precision and consistency that this tool can offer. I remember my first project using a wet saw, the way it sliced through the stone like a hot knife through butter – it was almost therapeutic.

2. Angle Grinder

The angle grinder is my go-to tool for those tricky, intricate cuts. I still remember a project where a complex design called for precision that only an angle grinder could provide. It required a steady hand and a lot of patience, but the end result was worth it.

3. Jigsaw

For those long, broad strokes, a jigsaw is an unbeatable companion. It’s kind of like a marathon runner – it keeps a steady pace and gets the job done efficiently. I recall a time when I had to cut a large swath of countertop, and my trusty jigsaw was the perfect partner for the job.

Factors to Consider when Choosing a Method

There are several factors to consider when choosing a cutting method – the type and thickness of the stone, the complexity of the cut, and even the time you have on hand.

I learned this the hard way when I chose a wet saw for a job that required the finesse of an angle grinder. The result was far from perfect, but it was a valuable learning experience.

Safety Tips for Each Method

Safety is paramount when handling these tools. For wet saws, always wear waterproof gloves and goggles to protect against flying debris.

With angle grinders, ensure you have a firm grip on the tool and use a guard to prevent accidents. For jigsaws, always use a safety guide and never force the tool. Remember, it’s not just about getting the job done, it’s about getting it done safely.

Cutting the Onyx Countertop

Step-by-step instructions for chosen cutting method

For cutting an Onyx countertop, my go-to tool is the angle grinder, particularly for its precision and control. Here’s the step-by-step process I follow:

  1. Mark the Cut: Start by marking the cut line on the Onyx countertop with a marker. It helps guide your cut and keeps you on track.
  2. Set Up the Angle Grinder: Next, attach a diamond-tipped cutting wheel to your angle grinder. This specific wheel works best for cutting through Onyx.
  3. Safety First: Before you start cutting, ensure you’re wearing safety goggles, gloves, and a dust mask to protect against flying debris.
  4. Start Cutting: Apply gentle, steady pressure to the angle grinder and start cutting along the marked line. Patience is key here. Rushing might lead to mistakes.
  5. Cool Down: Remember to periodically cool the blade with water to prevent overheating.

Tips for maintaining precision and avoiding mistakes

Precision is crucial when it comes to cutting an Onyx countertop, and here are a few tips I’ve learned over time that help avoid mistakes:

  • Keep the angle grinder’s speed at a medium level. Too fast, and you risk making a wrong cut. Too slow, and you might not cut through.
  • Always keep extra blades on hand, as the Onyx can wear down the blade quickly.
  • Maintain a consistent pressure on the angle grinder. Applying uneven pressure can result in an irregular cut.

Ensuring smooth edges and corners

Creating smooth edges and corners is the final, yet vital step in the process. Here are my tips:

  • After the initial cut, use a diamond polishing pad to smooth the edges. This removes any sharpness and gives the countertop a professional finish.
  • For the corners, use a round-over bit to create a perfectly curved edge. Remember, take your time and be gentle to avoid damaging the countertop.

Cutting an Onyx countertop can be a challenging task, but with the right tools and a patient approach, you can achieve a professional finish.

Just remember, it’s not only about getting the job done, but also doing it safely and precisely!

Trimming and Shaping

Once you’ve made the initial cuts, the next step is trimming and shaping the Onyx countertop to fit perfectly in your space. Here’s how I do it:

Techniques for Trimming Excess Material

I remember when I was working on my first Onyx countertop, I was a little nervous about trimming the excess.

I learned that it’s all about using the right technique. I’d recommend using a diamond blade for this job, as it cuts through Onyx like butter.

Start from the outside and work your way in, always following the marked line. It’s okay if you don’t get it perfect the first time, you can always go back and trim off more if needed.

Shaping the Countertop to Fit Your Space

Shaping was my favorite part of the whole process. It’s where you really get to customize the countertop to fit your space.

I recall being in a situation where I had to fit an Onyx countertop into a space with an awkward angle. I used a template made out of cardboard to mark the shape on the countertop.

Then, I used a stone saw to make angled cuts. It worked like a charm!

Polishing and Finishing Touches

The last step, polishing and adding the finishing touches, is what really brings the Onyx countertop to life. I still remember the first time I polished an Onyx countertop – the shine was nothing short of amazing.

Here, I use a diamond polishing pad starting with a coarse grit to get rid of any remaining unevenness, and then gradually move to a finer grit for a shiny, smooth finish.

It’s always such a rewarding moment to see the stunning end result of the hours put into creating the perfect Onyx countertop.

Safety and Health Precautions

Proper Ventilation and Respiratory Protection

I can’t stress enough the importance of working in a well-ventilated area when dealing with Onyx.

On one of my early projects, I underestimated the amount of dust that cutting and polishing the stone would create.

I quickly realized the necessity of a good ventilation system to ensure the dust doesn’t linger in the air.

Additionally, using a quality respiratory mask is a must. It’s an investment that has paid off for me over the years, protecting my lungs from harmful dust particles.

Eye Protection and Safety Glasses

A lesson I learned the hard way during my early days of countertop making was the importance of eye protection.

A stray chip of Onyx flew into my eye during a particularly intense cutting session. That incident taught me a valuable lesson.

Now, I never begin work without my trusty safety glasses. They’ve saved my eyes from potential injuries countless times.

Ear Protection

The noise generated from cutting and shaping the Onyx can be surprisingly loud. I remember working on a project for hours, not realizing the toll the noise was taking on my ears until I finished and found my ears ringing.

Since then, I’ve made a point of wearing ear protection. It not only protects my ears from potential harm, but also makes the work process more comfortable.

Avoiding Dust Exposure

The dust produced when working with Onyx isn’t just a mess to clean up, it can also pose a health risk.

I remember a time when my clean up was insufficient, and I ended up with a layer of dust over almost everything in my workshop.

This not only created extra cleaning work, but also exposed me and others in the workshop to harmful dust.

Now, I take additional measures to avoid dust exposure, such as using a wet saw for cutting and regularly cleaning my workspace.

Fire Safety Measures

While fire may not seem like an immediate concern when working with stone, safety should always be a priority.

I keep a fire extinguisher in my workspace at all times. This practice was reinforced when a neighboring workshop caught fire due to faulty electrical wiring.

Add to this the flammable nature of some of the products used in polishing, and you can see why it’s better to be safe than sorry.

Cleaning Up

Proper Disposal of Waste Materials

As a craftsman, I can tell you that all those shards, scrap pieces of Onyx, and dust do not belong in a regular trash can.

I learned this the hard way when I tried to remove the trash bag only to have it tear open, releasing a cloud of dust and scattering shards everywhere.

Since then, I’ve started using a dedicated waste disposal system for Onyx. I separate and recycle what I can, but for the waste that I can’t recycle, I use specified waste disposal services.

This not only minimizes the environmental footprint of my work but also saves me from the hassle of handling sharp shards and inhaling dust.

Cleaning the Workspace

Keeping the workspace clean is not just about aesthetics; it’s about safety. One particular incident comes to mind where a small shard, overlooked during cleaning, ended up causing a minor cut to my hand.

That was an unwelcome reminder for me to always thoroughly clean my workspace post work. I now use a high-powered vacuum cleaner designed for workshops to ensure I remove even the smallest pieces of debris.

And for the dust, I use industrial-grade air purifiers to maintain a clean and healthy air quality in the workshop.

Maintenance of Tools

Maintaining your tools is as important as maintaining your workspace. I learned this lesson early on when a poorly maintained saw caused me to make an inaccurate cut, ruining a piece of Onyx and hours of effort.

From that day forward, I’ve made it a point to regularly clean, inspect, and service my tools. I oil the moving parts, sharpen the blades, and replace any parts that show signs of wear or damage. This not only extends the life of my tools but also ensures they are safe and efficient to use.


As I look back on my journey with working with Onyx, I can see clearly the pivotal role that safety and proper maintenance have played.

From the waste disposal system that has saved me from the hazard of dust and shards, to the dedicated cleaning process of my workspace that prevents accidents, every step has been an important one.

Not to mention the routine maintenance of tools, which secures both the longevity of the tools and the efficiency and safety of my work.

Safety in a workshop can never be overemphasized. I have learned this through painful and sometimes costly experiences. It’s easy to overlook a small shard or to delay tool maintenance due to time constraints, but the potential consequences make these tasks vital.

Safety isn’t just about avoiding immediate harm, it’s about creating an environment where you can produce your best work without fear or hesitation.

In my early days, I often found myself in situations where I was unsure how to proceed. I can’t stress enough how valuable it was to seek professional advice in those moments.

If you’re unsure about operating a tool, maintaining your workspace, or safely handling and disposing of materials, don’t hesitate to ask a professional.

Their knowledge and experience can provide you with the confidence and the safety you need to proceed. Remember, there’s no harm in asking, and your safety is always worth it.


Hi! I’m Kobby, one of the co-owners of and the newest house owner in town. I’m a huge fan of most things natural. Over here on this site, I'm happy to share all the exciting hacks, tricks, and tips I have learned and continue to learn each day about taking care of natural stones.

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