Natural Cleft vs. Thermal Bluestone
Which Type Is The Right Choice For My Project?
Customers often ask us what are the different types of bluestone they can use for their walkway & patio projects. Luckily there’s only two options so it’s not a very difficult decision process! The options are either Natural Cleft Bluestone or Thermal Bluestone.
So let’s delve into the differences between natural cleft & thermal bluestone. Both types start as large blocks extracted out of the quarry. The natural cleft blocks originate closer to the surface of the quarry, and the thermal material comes from deeper parts. Natural cleft and thermal stone are both natural stone, they are just manufactured a little differently.
Natural Cleft Bluestone– Natural Cleft Bluestone is the more “classic” splitface stone with positive & negative projections (aka cleft) on the top and bottom surfaces. It is a non-slip paving stone suitable for all outdoor and indoor projects.
Natural cleft bluestone is split on natural fissures that exist within the quarried blocks. This splitting process is what creates the positive and negative projections or “cleft” of the stone. Because natural cleft stone is split, it will also vary in thickness. For example, the average 1″ thick natural cleft stone varies anywhere from 3/4″ to 1 1/4″ in thickness, & the average 1 ½” thick natural cleft stone varies anywhere from 1 ¼” to 2” in thickness.
Natural Cleft Bluestone is available in two color ranges – Full Color, or Blue/ Gray (photos of the natural cleft stone can be seen here- https://robinsonflagstone.com/pa-flagstones/full-color-range-natural-cleft-pa-flagstone & https://robinsonflagstone.com/pa-flagstones/bluegray-range-natural-cleft-pa-flagstone )
Thermal Bluestone- Thermal Bluestone has a smoother, thermal/ flamed surface. It is more consistent in thickness, size, & square than the natural cleft material. It is also a non-slip paving stone suitable for all types of projects.
The thermal bluestone is saw-cut to an exact thickness (1”, 1 ½”, etc.), and the surface is then flamed with a blowtorch to create a little bit of texture on the face of the pieces. Due to it’s consistent thickness and squareness, the thermal material tends to be a little easier to install than the natural cleft.
Thermal bluestone is available in two color ranges – Variegated or Blue/ Gray (additional photos of the thermal stone can be seen here- https://robinsonflagstone.com/pa-flagstones/thermal-paving)
In conclusion, picking the preferred type of bluestone for your project is pretty easy. First you need to decide if you want natural cleft or thermal bluestone, then you just have to choose your preferred color range. Either type of bluestone is perfectly suitable to use for any type of paving application. There is no right or wrong choice, it’s 100% personal preference.