Soft (2-5 Mohs)
Measurement of hardness scale, or Mohs, is used to evaluate the hardness of a mineral or rock, each kind being assigned a number, with talc numbered 1 and diamond 10.
Ranges in colour from ivory and soft greys to golden browns; absorbs oil and other liquids; easily scratched; acid sensitive; needs a penetrating sealant (siloxane/fluoropolymer); should be cleaned with pure soap (without synthetic ingredients) or neutral pH detergent.
Good for: Flooring and shower areas. For floors, it is best to choose a non-reflective finish. For showers, pick dense varieties with low absorption.
Local varieties: Blue/brown Kota, black Cuddapah, yellow Shahbad, lime green, among others.
(left) Local sandstone clads the exterior walls of this Atelier dnD-designed guesthouse for Jindal Saw Ltd in Bhuj, Gujarat. Photo Courtesy Atelier dnD. (right) Red travertine expands across all planes and surfaces of this bathroom in a home designed by Rajiv Saini and Associates. Photo by Sebastian Zachariah; Courtesy RS+A
Soft, easily scratched
Wide variation in composition; low to medium absorption of oil, water and other liquids; needs sub-surface oil repellent sealants; should be cleaned with neutral detergent or pure soap.
Good for: Roofing and exterior paving. Higher grades make good roofing as the slabs are thin, much longer lasting than synthetic roofing and cost-effective. Slate usually has a rustic finish, but milled or smooth products make excellent paving. Local varieties are comparatively dense.
Local varieties: Himachal white/green/black, multicoloured, silver shine, silver-white mica, kund peacock, Deoli green.
Relatively soft (6-7 Mohs)
Typically light browns, yellows and shades of red; absorbs liquids; is brittle; needs a penetrating sealant (siloxane/fluoropolymer); should be cleaned with pure soap or neutral detergent.
Good for: Used in gardens and commercial landscaping as well as exterior wall cladding, panels, pillars, sculptures and arches. Some forms of sandstone are more resistant to weathering; others are easier to work with (can be chiselled and dressed into a smooth surface or carved). Sandstone is durable, being acid- and heat-resistant.
Local varieties: Jaisalmer yellow, Dholpur beige, Mandana, Raj green, Agra red, Kandla grey, fossil.
Soft (3-4 Mohs)
From white and cream through reddish colours to deep mahogany, usually attractively banded or veined; absorbs oils and other liquids, easily scratched, acid sensitive; needs penetrating sealant (siloxane/fluoropolymer); should be cleaned with pure soap or neutral detergent.
Good for: Flooring as well as backsplashes. It is a very sturdy stone. Travertine is also becoming an increasingly popular cladding material.
Besides its chic, marble-like appearance, once sealed, travertine tiles are extremely low maintenance. The stone is available in a number of finishes: polished, unpolished, cross cut, regular cut, honed (filled or unfilled), tumbled, distressed edge, patinato.
Hard (7-8 Mohs)
A variety of colours from creams and browns to blues and greens; absorbs oils and other liquids (absorption properties vary across varieties); is brittle; sub-surface sealants such as oil repellents are recommended; should be cleaned with neutral detergent or pure soap.
Good for: The word “granite” originates from Latin granum and refers to the grainy structure of these crystalline rocks. Being harder and cheaper than marble, granite is often used as floor tiles and countertops, as well as in foyers and bathrooms. It can be shaped, yet has a high resistance to abrasion and scratching. Being the hardest of commercially available polished stones, granite is used in high-traffic situations. Contradictory to popular belief, though, polished granite is quite absorbent. Also, stress fractures caused by flame finishing make flamed granite very absorbent. Be careful not to place extremely hot things directly on granite, as temperature differentials can lead to cracks in the stone.
Local varieties: Imperial white, Kashmir white, Black Galaxy, Black Pearl, Desert Brown, Tropical Green and Sapphire Blue, among others.
Soft (3-5.5 Mohs)
Absorbs oil and other liquids; easily scratched, acid sensitive; needs a penetrating sealant (siloxane/fluoropolymer); should be cleaned with pure soap or neutral detergent.
Good for: This metamorphosed limestone is a very popular flooring material. However, it requires a high level of maintenance in high-traffic areas. Non-reflective finishes work well as flooring. Polished marble is ideal for vertical application, such as walls. Its softness and homogeneity make it much sought after for sculptures and buildings too.
Local varieties: Indian types include Makrana white, Rajnagar white, forest green, emerald green, Bisdar brown/green, golden green, Katni green.
(Left) Tiles of khareda, a stone from Madhya Pradesh, create a smooth flooring in this living room of a home designed by Rajiv Saini and Associates. Photo by Sebastian Zachariah; Courtesy RS+A. (Right) Strips of Cuddapah cover this wall that is part of a passage in a home designed by architect Vivek Prabhu. Photo by Pradnya Gulawani
Hard (4-7 Mohs)
Absorbs oils and other liquids; brittle; needs sub-surface sealants (oil-repellent type); should be cleaned with neutral pH detergent or pure soap.
Quartzite is metamorphosed sandstone, usually white or grey in its pure form. Other colours (shades of pink, red, yellow and orange) result from impurities.
Good for: Quartzite is a very strong stone, but is not often found in large enough quantities of uniform colour suited for making into slabs. It is used as paving blocks, railroad ballast, rubble, crushed stone and roofing granules.
What to use where
Flooring: Choose from Kota, Jaisalmer, Cuddapah, granite or marble. Kota, Jaisalmer and Cuddapah are inexpensive, but can’t be polished to as high a shine as marble. “Aesthetically, Kota, Jaisalmer and Cuddapah are best suited for an earthy look. Granite and marble are ideal if price is not an issue. But all marbles cannot be used for flooring,” says architect Aanchal Nath. For a sharp look, choose polished granite. It can be used in high-traffic zones as it requires less maintenance. Another option is slate. This rough, textured grey stone has a rustic appeal, ideal for verandas and decks.
Wall cladding: The purpose is mostly decorative, not functional, so any stone, including soft and flaky slate and sandstone, can be used. Marble variants such as travertine, a semi-porous stone, are aesthetically appealing, as are semi-precious onyx and mother-of-pearl surfaces; but owing to their high price, these are usually used as borders, accents or inlays. Granite is a more durable option.
Counters: Hardness, texture and stain resistance make granite the best value for money on kitchen counters. Porosity is a critical factor: Most marbles do not react well to acidic substances, which make them less suitable in the kitchen. Avoid Katni for countertops: It is very soft and its edges tend to chip unless tapered. Bathroom counters can be done in marble, granite or even Jaisalmer, depending on whether you want contemporary gloss or earthy appeal. “Some people use black Cudappah for counters. However, this isn’t a recommended material as it is porous and stands the risk of fungal growth,” says architect Navneet Malhotra.
Furniture: Pick granite, marble or onyx for tabletops. Inlays can be semi-precious stones such as jasper or tiger eye. For pedestals, choose between granite and marble.
Flooring: Kota, Cuddapah, Jaisalmer and granite are recommended by Nath. Although the first three are not as hard as granite, their low pricing makes them ideal for large areas. When it comes to finishes, granite displays great versatility. Slate is also a good option.
Cladding: “You can choose between Jaisalmer, Dholpur, granite or marble. Granite is best suited for contemporary designs. It is also the easiest to maintain,” says Nath. Architect Nilanjan Bhowal suggests Agra stone, slate and Italian marble.
Text: Sonali Mathur
Inputs: Architects Navneet Malhotra, Aanchal Nath and Nilanjan Bhowal
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