Polished
Natural stones are polished through the application of abrasive material by polish heads that gradually are changed from coarse to fine. This technique brings out the colour and properties of the polished natural stone.

Natural
A natural finish implies the absence of treatment. It is used exactly as it is extracted, leaving the finish as natural as possible. This finish is mostly used for cladding and cobblestones.

Aged
This treatment involves vibrating the surface of the stone to mimic ageing. Although there are many methods used to go about this treatment, generally all of them lead to a soft surface.

Tumbled
Tumbled is also an ageing treatment to achieve an antique finish. In this case, a vibrating drum-like machine uses finer, more resistant stones, to wear out the surface of the natural stone. This leaves an aged finish and generates a soft surface.

Bush Hammered
This finish is achieved by hitting the surface of the natural stone with a tool called bush hammer. It generates an uneven surface creating craters of different sizes. Through this method, the surface becomes slip-resistant and is used ideally for dense traffic areas.

Sand Blasted
This finish falls in the same category as bush hammered. The surface of the natural stone is blasted with small silica particles using an air gun. This creates little craters on its surface, highlighting the colour of the stone and creating a more slip-resistant finish.

Mushroom
This finish is generally achieved by manual tools which through controlled blows, chip the surface of the natural stone. This creates a rustic appearance, enhancing the texture and irregularities.

Leather
This is achieved by brushing the surface of the natural stone by various brushes. This results in a surface which is soft, warm and smooth to the touch. Very few stones can be treated using this method, including granite.

Flamed
This is done by exposing the surface of the stone to a high-temperature flame. This creates roughness and makes it suitable to withstand exterior use.

Sawn
This is achieved using a diamond disc tooth saw. The surface of the stone is sawn to create a rough and irregular finish. This makes the overall stone lighter and gives it a non-glossy finish. It is generally used for external paving, steps, pathways, driveways and patios.

What is natural stone? It is a stone that is dug up from the earth and is mainly quarried from a mountainous ground. There are many types of natural stones, including slate, granite, limestone, basalt, quartzite, marble, sandstone and travertine etc. The aesthetics and characteristics of natural stone are defined by the process of its formation, e.g. from rivers, from volcanoes, from tectonic folding. Each type of stone is unique as no two places on earth have the same exact geological forces. This also means that the same kind of stone from different areas can differ widely.

The three main processes that natural stone go through in the field of architecture and construction are quarrying, processing and applying.

Quarrying

The process of quarrying is defined as the extraction of these natural stone from the surface of the earth. It is done through different equipment’s and methods, e.g. hand-held tools, explosives and power saws. Hand tools are used when the stone lies in an easily accessible area. The main hand tools are the drill, hammer and wedge. A row of holes is made through the drill and wedges are places within these holes. These wedges are hit with the hammer until it forces the stone to crack along the drilled row of holes. This method is known as the plug and feathers. Explosives and power saws are commonly used for detaching large stone blocks which are then broken down into smaller pieces through the plug and feather method.

Processing

After quarrying the natural stone is in the form of slabs. The slabs can be made of a dimension by sawing. There are many natural stone saws that include diamond-covered blade, gang sawing, straight saw blades and various circular saws. After sawing the next step is to polish the surface of the stone. This is done by using different polish heads, starting from coarse and then slowly moving onto more finer grit abrasives until the surface of the stone is glossy and polished. This way, the stones‘ natural texture and the colour are enhanced. Other than this, there are many stone finishes that can be done, including chiselling, sandblasting or heat and flame treatment.

Application

Natural stone is extensively used in the construction industry. Their characteristics have made them one of the most favourite construction materials for humans since many thousands of years. Owing to this, its application has always been diverse. Since many years natural stones were traditionally used in masonry, decoration, indoor flooring, roofing etc. The use of them in veneering for stone wall cladding and facades is an element of modern architecture which has evolved from traditional masonry.

Mechanical properties and resistance
Basalt is a tenacious rock, with the evaluated hardness of 6 on the Mohs’ scale, which puts it in a strong-to-very strong category. Empirically proven, the values of all three strength properties are impressive, compressive (100-300MPa), tensile (10-30MPa) and sheer (20-60MPa). As silica makes up for about 50% of basalt’s structure, it is quite dense material, at 2.6-3.0g per cube centimetre. Basalt products are incredibly hard-wearing and resistant. The resistance goes further than the pure flexural strength, as it offers unparalleled abrasion and chemical resistance. Hence the basalt tiles are often used for flooring of heavy industrial objects. Finely polished, these floors also feature a metallic sheen.

A wide variety of applications
Since Roman times, basalt has been used as a construction material, usually for building cobblestone roads. Nowadays, basalt is most commonly used in its crushed form, as it can serve many purposes. Road bases are often made of crushed basalt; it can be a concrete and asphalt pavement aggregate or filter aggregate for drainage fields. Stone wool – a renowned thermal insulation material – can be produced from heating and extrusion of basalt.

Armenian basalt as a dimensional stone
Being a winsome rock, basalt is often cut into sheets, slabs, or bricks, and then used for decoration purposes. Due to its hardness and resilience, but also low porosity, basalt makes a perfect, long-lasting paving material. The density of the rock makes it a great choice for not only walkways and patios, but also driveways, and stairs. It comes in a variety of finishes, shapes and sizes, each providing unique textures. While the most popular finish is flamed, it also can be chiselled, sandblasted, honed or polished. Contemporary architects like using basalt pavers due to its somewhat unusual appearance. The usual thickness of basalt pavers ranges from 1-1/2” up to 6”, depending on the surface it’s installed on.

Basalt tiles can also be used for both indoor and outdoor wall cladding. The benefits of cladding the walls with natural stones are additional strength and durability, but also the aesthetic appeal. The notable traits of basalt besides the aesthetics are extremely high insulating properties and fire resistance.

Regarding indoor decoration, basalt is commonly used in the form of floor or wall tiles, usually flamed or honed, measuring from 3/8” to 3/4” thick. The black or dark grey tiles create a mesmerizing visual effect in contrast to other natural materials, such as wood for example. Basalt can also be used for veneering but is also cut into thicker basalt slabs. These can be polished to a shiny black lustre or flamed – adding a beautiful texture to this natural stone. Basalt is dense, durable and long-lasting material for both outdoor and indoor projects.

Basalt has a wide variety of purposes in Architecture and construction projects. In construction it could be used as crushed aggregate for road base, asphalt pavements, railroad blast and many other purposes but it has a long record of being used as a building stone especially throughout the Roman Empire from different architectural projects to stadium seating and even hardscaping as these are highly resistant to abrasion and acid.

Basalt could be made into different dimension stones. These stones are cut into thin slab or blocks and polished to use as floor tiles, monuments, buildings veneers and other projects. It could also be used to make columns, Lumineers, benches and even on the facade.

Basalt comes in different finishing’s including Sawn w/o blade traces, Honed, Polished and Bushhammered. These tiles in different cladding, surfacing and size appeal to the eyes. That’s why this stone could enhance the appearance of the buildings as well as landscaping when combined with other stones to form a unique contrast.

Natürlich hat jeder Naturstein seine besondere Beschaffenheit, und die eine oder andere Unregelmäßigkeit gehört quasi zum guten Ton, schließlich ist es ein Naturprodukt. Nichtsdestoweniger beginnt die Qualitätskontrolle mit dem Beginn einer potentiellen Geschäftsbeziehung. Wie läuft das bei uns in der Regel ab:

Wir setzen größten Wert auf persönlichen Kontakt, daher ist ebendieser gemeinsam mit einem Besuch der Produktionsstätten unabdingbar. Hier durchlaufen wir gemeinsam mit dem Lieferanten-in-spe eine Reihe von Checklisten, wie zum Beispiel Arbeitsbedingungen, Art und Qualität der eingesetzten Maschinen und selbstredend die Qualität der Steine. Läuft hier alles nach Plan, und möchte auch der Lieferant mit uns zusammen arbeiten, geht es in die zweite Runde:

Die Erstbestellung. Üblicherweise bestellen wir eine kleine Menge an Natursteinen, um feststellen zu können, wie gut der Durchlauf Bestellung – Lieferung funktioniert, v.a. in der jetzigen Situation ist es wichtig, Lieferengpässe oder logistische Probleme rasch zu erkennen. Abgesehen davon wollen wir natürlich auch sicher stellen, daß die Qualität der gelieferten Steine auch der Qualität der Steine vor Ort entspricht: Sind die Maße der Steine innerhalb vernünftiger bzw. während der Kalibrierung vereinbarten Abweichungen? Wie hoch ist der Ausschuß von Beginn an, was sind die Ursachen für diesen? Dazu muß gesagt werden: Eine de facto perfekte Lieferung gibt es nicht – wie oben angesprochen, sind es Natursteine. Kleinere Bruchstellen oder Brösel gibt es immer, die Frage ist aber, ob der Stein noch ohne Verzicht auf Qualitätsansprüche für den ursprünglich gedachten Zweck verwendet werden kann.

Verlegen Sie beispielsweise Marmor als Boden und sind an der Unterseite hie und da kleinere Ausbrüche, ist das im Rahmen vertretbar. Ziehen sich die Bruchstellen oder Schäden aber beispielsweise hin zur Trittfläche, ist dies nicht mehr akzeptabel, da es nicht der Natur des Steins entspricht, Löcher oder fehlende Ecken zu bilden.

Der Stein kann natürlich während des Transports beschädigt werden, in der Regel werden diese aber so verpackt und mit solchen Speditionen versandt, daß dies weniger eine Rolle spielt. Im Bild oben ist Marmor zu sehen, der bereits beim Zuschnitt in der Fabrik beschädigt wurde. Bruchstellen dieser Art deuten auf mangelnde Qualität der Maschinen oder unsachgemäße Handhabung beim Ablegen und Vorbereiten für den Versand. Mindestens 3 der 10 Steine sind nicht weiter verwendbar – außer als Muster – und weitere drei nur noch bedingt verlegbar (wenn man wirklich auf top Qualität setzt). Ein Weiterverkauf dieser Charge an Kunden ist ausgeschlossen.

Um genau diese Probleme für unsere Kunden zu vermeiden, ist ein tiefgehender Qualitätscheck unvermeidbar. Denn erst, wenn alle Kriterien erfüllt sind, nehmen wir einen Lieferanten als solchen auf.

Weight per unit of volume = the ratio between the weight and the apparent volume of the stone which corresponds to its actual weight. This also includes the holes inside the natural stone, i.e. its porosity. This is fundamental in the assessment of the loads that a particular natural stone exerts on the fixing and supporting structures. It also provides information on the compactness of the same.

Imbibition coefficient = a natural stone’s capacity to absorb liquids – this gives an indication of its porosity. This coefficient is especially important when the stone is going to be frequently in contact with liquids as is the case in bathrooms, kitchens, exterior uses, etc.

Compression breaking load = the stone’s ability to withstand loads. This is important for natural stone worked into shapes that serve a structural function such as columns, arches, etc., but it is also important for cladding and flooring, which, for many reasons, are subjected to compressive stress.

Compression breaking load after freezing = a natural stone’s ability to withstand loads in environments with significant temperature changes above and below zero degrees Celsius. This is a fundamental parameter when the stone is supposed to be used in environment that undergo significant temperature changes within 24 hours or that have frequent temperatures considerably below the Celsius freezing point.

Flexural strength = a stone’s ability to withstand bending pressure. This is extremely important because mechanical stress will always cause direct or indirect bending at least to some extent.

Frictional wear test = the natural stone’s ability to withstand continuous wear. This is essential in assessing a stone’s suitability for internal and external flooring, shelves, etc.

Die sogenannte Mohs Härteskala ist eine Skala von 1 bis 10, wobei Steine mit höherem Härtegrad jene mit niedrigerem kratzen und ritzen können. Es ist also eine relative, keine absolute Skala.

Als härtester Stein gilt bekanntlich der Diamant mit einem Härtegrad von 10, aber wie sieht es mit jenen Steinen aus, die man üblicherweise für Fliesen, Fassaden o.ä. verwendet?

Marmor ist beispielsweise ein relativ weicher Stein – was ihn natürlich auch für Bildhauer beliebt macht, nebst seiner vielfältigen Einsatzmöglichkeiten im Bau- und Wohnbereich. Marmor hat in etwa einen Härtegrad von 3. Damit ist er gerade einmal härter als Gips oder Alabaster und kann auch mit Messing- oder Kupfermünzen geritzt werden. Auch Travertin hat einen Härtegrad von 3! Generell haben Kalksteine in der Regel eine Mohs Härte von 3, manchmal 4.

Basalt hingegen ist ein deutlich härterer Stein: Er erreicht jedenfalls Mohs Härte 6 bis 7, und hier wird schon Hartmetall-Werkzeug notwendig, um ihn zu bearbeiten. Ähnlich hart wie Basalt ist dann auch Andesit.

Schlußendlich haben wir noch den Granit mit einer Härte von 7 nach Mohs. Die Bearbeitung von Granit erfolgt in der Regel mit Werkzeugen, die zumindest Korund (Härtegrad 9) oder Diamanten (Härtegrad 10) enthalten, wobei derartige Schleif- und Trennwerkzeuge natürlich auch Gesteine niedrigerer Härte bearbeiten können.