ZEINTZUK DIRA HARRI NATURAL BIGARRENAK ETA NON ERABIL DAITEZKE? paisaia harria

Zergatik dira batzuk harri naturalak considered to be soft when they all appear to be hard? The answer lies within ‘relative’ hardness. Mohs scale of hardness was invented in 1812 and compares the relative hardness of ten minerals. Diamond is the hardest and rates a 10, while granite is the toughest natural stone at 6. Limestone comes in at 3 as does its metamorphic counterpart, marble. Softer stone is easier to dress or carve but does not wear or weather quite as well as harder stone. Here we discuss some of the more popular soft stones along with suitable applications.

Harri irregularrak

Arroka sedimentarioa

Kareharria, hareharria eta eskistoak dira arroka sedimentario mota ohikoenak. Hauek milioika urtetan zehar presio izugarriaren bidez sortu ziren, ozeano-hondora eroritako sedimentuari eraginez.

Arbela

The layers in slate are described as being “foliated” and they are easily split apart to create whatever thickness is required. UK slate is considered to be hard and was traditionally used as roofing, while soft slate is found in China, Spain, Italy and the USA. With a broad range of natural slate colours, a multiple array of designs can be achieved, from contemporary to classic, rustic to refined. Slate is often recommended for high traffic areas, thanks to its remarkably durable composition. It is also non-porous and does not easily react with acid liquids. It is fire proof, weather resistant and achieves good slip resistance dues to its riven finish.

Kareharria

Limestone is a very common building material and is formed mainly from the mineral calcite, derived from the calcium in bones and seashells deposited over the millennia and forced together through pressure. While it also contains magnesium, it is harder and more weather resistant, and can also be polished. Portland stone from the eponymous island in Dorset is probably the single most famous type of limestone and was used to build many of London’s great buildings. It is used for external cladding as well as paving, fireplaces and other internal and external decorative features. Its soft colours are its trademark visual attributes.

Hareharria

Hareharria izan zen ziurrenik 1800. urtea baino lehen gehien erabiltzen den eraikuntza-harria, zubietatik hasi eta eraikin dotoreetaraino. Bere izenetik ondoriozta daitekeen bezala, harea, materia organikoa, kaltzita eta beste hainbat mineral elkarrekin fusionatu zirenean sortzen da milurtekoan zehar presio ikaragarrian. Testura lodia edo finarekin eskuragarri dago eta tradizionalki akabera matean ematen da. Batez ere krema, gorria edo grisa Erresuma Batuan, bere kolorea barruan dauden mineral gehigarrien araberakoa da. Silizeak zuritasuna ematen du, eta burdinak, berriz, kolore gorrixka bat emango du. Bere aplikazio-eremu nagusiak hormak eta zoruak, edo kanpoko zoladurak dira.

Marmola

Marmola kareharriaren eratorria da, milioika urtetan zehar bero eta presio kolosalaren metamorfosiaren ondorioz sortua. Beste harri batzuekin alderatuta nahiko biguna izan arren, marmolak oso ondo leuntzeko joera du. Tradizionalki marmola ateetan erabiltzen da eta goi mailako akabera sortzen laguntzen du.