“Oh my! I am completely confused looking aisle upon aisle of natural stone stock/inventory you have shown me.”

These are common expressions when a buyer visits first time at the premises of World of Stones USA. Not here, everywhere it happens when a buyer looks at ranks demonstrating a variety of stones even after touching many of those. It is true that the catalog mostly contains brand names of stones, which usually differ from one brand to another.

Thereby, our natural stone consultants got inspired to write a stone shopping guide as a reader-friendly post accessible on the web for all. The content of the natural stone buyer guide is as follows.

  • Stone Types
  • Applications
  • Properties of Natural Stones
  • How to Test Properties
  • Natural Stone Textures
  • Natural Stone Maintenance
  • Natural Stone Costing

Introduction to Natural Stone Types Based On Their Origin

If you are tech-savvy and use Google-like search engine to know about the origin of natural rocks, which we are quarrying and obtaining dimension stones for construction and other purposes, you may have come across three major geological terminologies:

  1. Igneous rocks: It comes from molten volcanic stuff like magma.
  2. Sedimentary rocks: It forms when eroded fragments of other rocks is settled and compressed in the crust of the earth.
  3. Metamorphic rocks: It forms when igneous and sedimentary rocks are transformed due to pressure and heat.

However, in the construction industry people are accustomed to only two segments of rocks:

  1. Siliceous rocks: Which contains Silica or sand as the major element. Quartzite, Granites, Slate, and Sandstone are ideal examples of it.
  2. Calcareous rocks: Which contains Calcium as the major element. Marble, Limestone, & travertine are following in this category. 

In industry, natural stones are used in different forms, such as:

Whole Stones

Cubes Slabs Veneer
Cubes Slabs Veneer
Cubes used as stacked stones as structural elements. Today, it is used in hardscapes only. Slabs used on floors and walls in moderate thickness in interior & exterior applications. Stone veneers are thin slices sticking on the wall surfaces, be it exterior or interior.

Crushed Stones: 

Gravel Pebble Cobble Boulder
Gravel Pebble Cobble Boulder
These are mainly used as hardscape elements in your landscape.

Defining Areas/Spaces for Natural Stone Applications

With the basic introduction, I hope now it is time to learn which stone type are the choices for different areas like interior, exterior, and landscape or hardscape. The major categories are:

Interior Spaces Exterior Spaces
The spaces are: Living room, bedroom, bath, toilet, mudroom, kitchen, staircase, storage, and other spaces.
The application areas are: Mainly floors & walls, kitchen countertops, cabinet-tops, tabletops, fireplace facing, etc.
The spaces are: Façade, porch, terraces, patio, pool decks, paths, walkways, and driveways are common spaces found.
The application areas are: pool and patio paving, stepping stones, exterior wall cladding, window sills, and headers.
Structural elements in stacked walls, columns, trims, pillars, and other internal surfaces. Architectural elements in stacked walls, trims, and posts;patio paving,in stone-based furniture.

If you are interested in details, we have prepared an Infographics to take a birds-eye view.

The Most Common Types of Natural Stones Used In the Industry:

The biggest trouble in the natural stone industry is colloquial naming. The majority of stones are known by their local names instead of their generic types. For instance, Bluestone and Flagstone are not generic or technical names but used based on some of their properties like colors and shapes.

Thereby, I have presented a short & sweet list of the most common and generic types of natural stones used in the present day in the US and elsewhere.

Siliceous Types of Natural Stones

Quartzite Natural Stone

Quartzite Natural Stone
Quartzite is a metamorphic type of rock. It has high silica content – nearly 90% of the total mass.

The Best Application Areas:

Interior Spaces

Kitchen countertops, cabinet-tops, tabletops, floors, and other heavily used surfaces including floors and stairs.

Exterior Spaces

Façade, porch, and patio paving. Pool decks, paths, walkways, and driveways.

Granite Natural Stone

Granite Natural Stone
Granite is a mostly igneous-origin type of rock, but in many instances, it is found as sedimentation-origin. It has high availability around the planet.

The Best Application Areas:

The same as Quartzite.

Sandstone Natural Stone

Sandstone Natural Stone
Sandstone is a sedimentary type of rock. It contains sand particles. It is available across the globe and many sea floors.

The Best Application Areas:

The same as Granite. It is highly used as the structural elements and architectural elements in the interior as well as exterior places.

Slate Natural Stone

Slate Natural Stone
Slate is a metamorphic type of rock. It contains volcanic ash and clay particles.

The Best Application Areas:

Due to fissility, it has limited applications but is considered as the best material for roof tiles. Exterior applications are many. It is the best choice as a paving material. 

Calcareous Types of Natural Stones

Limestone Natural Stone

Limestone Natural Stone
Limestone is a sedimentary type of rock. It contains calcite particles, so it is a calcareous rock. It is available almost everywhere under the land and sea surfaces.

The Best Application Areas:

It is highly used as a paving material for exterior applications. It is also used as a wall cladding material. It is used as roofing granules mostly in terraces and external paving spaces when a topcoat is of RCC material mixed with stones.

Marble Natural Stone

Marble Natural Stone
Marble is a metamorphic type of rock. It contains calcites particles, so it is a calcareous rock. It seems gorgeous when given glossy finishing/polishing.

The Best Application Areas:

It is a great choice for interior applications like flooring and wall cladding. It has tons of varieties and highly confusing to segregate. So, it is advisable to take help of our stone consultants.

Travertine Natural Stone

Travertine Natural Stone
Travertine is a sedimentary type of rock, but the formation is quite different from limestone. It forms from precipitates of calcites in caves of hot springs. 

The Best Application Areas:

It looks like marble and limestone, but cheaper and sturdy alternative. It has good applications as patio paving and pool decking apart from the standard flooring and wall cladding.

Learn About the Different Properties of Natural Stones & How to Test It with Simple and Handy Tools

If you want your natural stone material for a long service lifespan within the surrounding environment contexts, durability is the term used for it. According to common sense, stones in the construction industry have the following kinds of possible threats.

Impacts: 

  • Hit by other strong objects,whether by accident or intentionally. 
  • Structural load, be it dead or live traffic.
  • Earthquake, a storm like natural disasters.

Climate:

Heat, cold, wind, humidity, rain, frost/thaw cycle, and Sunrays

Chemicals:

Water, oil, acid rain, spills, corrosion, sewage, pH fluctuations, and carbonation.

The results of these threats are:

  • Splitting 
  • Crumbling 
  • Cracking 

Metrics of Durability:

The American Society for Testing and Materials has defined the following metrics to measure durability factor in for the construction material, including natural stones. However, it is pure scientific terms, and you might get puzzled by it, so I have tried to simplify it the most possible ways.

  • Absorption and specific gravity 
  • Modulus of rupture 
  • Compressive strength 
  • Flexural strength 
  • Abrasion resistance 

How to Measure Durability?

Applied geologists take help of testing laboratory to measure the durability factors of natural stones by taking various approaches, including:

  • Accelerated Laboratory Durability Tests: freeze-thaw cycling, wetting–drying, and salt crystallization resistance.
  • Environment Tests: complex environmental testing in test cabinets.
  • Exposure site testing.

Unfortunately, an ordinary client cannot afford to pass through such testing and mostly rely on the results hanging on the walls of the office of stone supplier or distributor. Now, I am going to give you some practical and handy tools and methods to measure various parameters of durability factors in the natural stone industry.

Tests Description Units for Results/value
Water Absorption The ability of the rock to soak water. Percentage (%)
Hardness It refers to the strength of the rock. Units on Moh’s scale
Density Density is the mass per unit volume of a substance. Kg/cm3
Loss on Ignition A small quantity of quartzite is heated, thereby letting the volatile substances be released.  Percentage (%)
Flexural Strength It is the property of the rock which defines its ability to defy stress N/mm2
Compressive Strength It is defined as the load that the rock can withstand without undergoing distortion. N/mm2

 

Hardness Tests:

Moh’s Scale is used to test the hardness of the construction material.

Minerals in Stones Moh’s Scale Hardness Test creating scratch on the glass surface

By creating scratch on the glass surface.

Talc  1 Easy to scratch with thumbnail 
Gypsum  2 Tough to scratch with thumbnail 
Calcites  3 Easy to cut by a knife
Fluorite  4 Somewhat tricky to cut by a knife
Apatite  5 Difficult to cut by a knife making scratch using a steel knife

By making scratch using a steel knife.

Feldspar  6 Tougher to cut by a steel knife 
Quartz  7 Not cut by a knife
Topaz  8 It can scratch glasses or softer material 

Water Absorption or Porosity Tests:

The density of pores defines the water absorption capacity of the stones. Thereby, if you want to know about the sensitivity of acids, stains, oils, or other liquid, knowledge of porosity may help you a lot. So, I have listed some of the major stone types and their water absorption metrics here.

Stone Types Water Absorption (In Weight %) Standard Requirements porosity of stone

You can test the porosity of stones by sinking a portion of those into food colored water.

Granite 0.8-1 0.40
Marble 0.8-0.04 0.20
Sandstone 12-0.3 8(S)

3(QS)

Limestone 26-0.08 12(LD)

7.5(MD)

3.0(HD)

Slate 6-0.3 0.45

Other approaches to test porosity and acid sensitivity of stones are:

sensitivity of stones sensitivity of stones 2 sensitivity of stones 1
Soak stone pieces in plain water for 15 mints.  In some stones, liquids puddle up on top of the surface, without soaking in it. Ordinary vinegar is sufficient to test acid sensitivity

 

Strength Tests:

Two kinds of tests used to know the strength of the natural stones:

Compressive strength

Stone Types Typical Compressive Strength (MPa) Standard Requirements measurement of the crushing load

It is a measurement of the crushing load.

Granite 300-100 131
Marble 150-80 52
Sandstone 120-10 27.6(S)

68.9(QS)

Limestone 150-4 12(LD)

28(MD)

55(HD)

Slate 200-25

 

Flexural strength

Stone Types Typical Flexural Strength (MPa) Standard Requirements rupturing capacity of rocks

It tests the rupturing capacity of rocks against bending strength.

Granite 30-6 8.3
Marble 22-6 7
Sandstone 15-3 2.4 (S) – M0R

6.9 (QS) – MoR

Limestone 21-2 2.9 (LD) – MoR

3.4 (MD) – MoR

6.9 (HD) – MoR

Slate 50-15 49.6 (MoR)

 

Abrasion Tests:

Abrasion of stones can take place due to scratching, scuffing, wearing down, rubbing away, or marring like processes. When you calculate the resistance to abrasion, consider the following things first.

  • Stone surface finishes 
  • Foot or vehicle traffic 
  • Tracking of particulates
  • Adjacent surfaces 
Abrasion Index Appropriate Uses
< 8 Good for interior or light exterior applications
8-12 The right choice for light exterior or commercial paving and interior flooring.
12-25 Suitable for general outdoor or commercial and indoor applications.
>25 The best selection for all types of applications, including high traffic exterior or commercial flooring.

 

Stone Types Typical Abrasion Index (Ha) Standard Requirements Typical Abrasion Index
Granite 50-150 25
Marble 15-50 10
Sandstone 4-24 2(S)

8(QS)

Limestone <1-20 10
Slate 4-20 8

 

Learn About Natural Stone Finishes Prevailing In the Industry 

Natural stones have their inherent rock textures, but finishing treatments can leave impacts positively by enhancing it. The following is the list of the most common stone finishes prevailing in the industry to know what the best is for you and where to apply which treatment.

Natural Finishing:

It is the absence of treatment to leave a stone in natural status. 

 Natural Finishing
Polished Stone Finishing:

You may have shining surfaces with it.

 Polished Stone Finishing
Tumbled Stone Finishing:

It gives aging effects and creates an antique look. 

Tumbled Stone Finishing
Bush Hammered Stone Finishing:

It creates different sizes of craters in uniformly distributed patterns. So, you will have non-slip surfaces.

Bush Hammered Stone Finishing
Sandblasted Stone Finishing:

It offers comparatively small craters to highlight stone colors, and give skid-free surface.

Sandblasted Stone Finishing
Leather Stone Finishing:

It brings undulating surfaces with a soft, warm, and smooth touch.

Leather Stone Finishing
Sawn Stone Finishing:

It provides surfaces with small furrows and undulations to give it a matte tone. 

Sawn Stone Finishing
Honed Stone Finishing: 

It gives a matte, flat, or satin look.

Honed Stone Finishing
Flamed Stone Finishing:

It creates a slight roughness on the top layers of the stone surface and renders it useful for outdoor applications.

Flamed Stone Finishing

Finally,

If you have any confusion regarding natural stone buying, our consultants are always available to assist you. Feel free to take their help online or in-person.

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