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Have you ever wondered what gives contemporary lobbies their cool, understated elegance? Pietra Grey Marble, quarried in Iran’s Lashtar region, delivers a deep‑charcoal base laced with fine white lines that feels both modern and timeless. Blocks are trimmed into wide slabs, typically three metres by 1.8 metres and 20‑ or 30‑millimetres thick, then polished, honed or brushed for different moods. With bulk density around 2.7 g/cm³ and water absorption below 0.2 percent, the stone balances beauty and strength. The result is a premium surface loved by architects designing luxury hotels, boutiques and calm residential spaces.
When quality matters, choosing the right partner can make all the difference. JAM Stone Co. has spent decades mastering every stage of Pietra Grey Marble, from controlled quarry extraction in Lashtar to precision polishing in its ISO‑certified factories. Automated water‑jet cutters, in‑house labs and veteran craftsmen work together to keep thickness tolerance within half a millimetre and gloss readings above 85 units. Global clients—architects, wholesalers and project developers—value the company’s careful crating and dependable shipping schedules. JAM Stone Co. ensures that every slab of Pietra Grey Marble meets the expectations of quality‑driven projects worldwide.
Pietra Grey Marble, also traded as Lashtar Marble or Pietra Grigio, is a metamorphic stone formed when limestone in central Iran was re‑crystallised under heat and pressure. The result is a dense, dark grey matrix streaked with sharp, almost parallel white calcite veins. Because the veins are generally thin and evenly spaced, slabs create a sleek, linear look prized in minimalist design. Mineral analysis shows roughly two‑thirds calcite with smaller amounts of dolomite and quartz, giving the marble its balance of visual depth and structural cohesion. Good polish retention and consistent colouring make it a go‑to choice for interior surfaces that must look refined yet stable.
Laboratory tests place Lashtar Marble among dense, low‑porosity marbles. Average bulk density is 2.7 g/cm³, open porosity sits below 0.5 percent and water absorption hovers near 0.17 percent, meaning the stone resists moisture when properly sealed. Compressive strength ranges from 84 to 96 MPa and flexural strength averages 12 MPa, values suitable for load‑bearing interior floors, stairs and counters. Still, reinforcing with substrate or metal ribs or specifying 30–40 mm thickness is recommended for spans > 900 mm. With Mohs hardness between three and four, the surface resists normal foot traffic yet remains workable for detailed edging. However, entrance mats and routine dust-mopping are recommended to prevent abrasive wear. All in all, these numbers confirm the stone’s reputation as a reliable structural and decorative material.
About 95–97 % calcite with ≤ 1.5 % dolomite plus trace quartz and iron oxides. Veins are filled mainly with pure calcite, keeping colour contrast sharp without heavy mineral staining. This balanced mix yields moderate hardness while retaining the warm, light‑reflective quality designers expect from a classic marble.
The base tone runs from anthracite to smoky graphite, always cool‑grey rather than brown. Veins appear as crisp, almost parallel white lines, 0.5‑2 millimetres wide, giving an orderly ‘pin‑stripe’ effect across the slab. Occasional smoky swirls add depth, yet the overall regularity makes book‑matching and large‑panel alignment straightforward for designers.
Bulk density averages 2.7 g/cm³, similar to many premium marbles. Open pores occupy about 0.47 percent of the volume, with water absorption below 0.2 percent. Such tight micro‑structure limits capillary staining and allows the stone to take a high, mirror‑like polish that stays bright in normal indoor conditions.
A Mohs scale value of three to four places Pietra Grey in the mid‑range of marbles, hard enough for foyer floors yet soft enough for clean fabrication. Compressive strength reaches up to 96 MPa, and flexural strength averages 12 MPa, supporting stair treads, vanity tops and wall panels under typical residential or light‑commercial loads.
Most Lashtar Marble blocks are compact, but occasional stylolites, clay seams or micro‑fissures below 0.2 millimetres can occur. Factories usually fill these with clear resin, then hone and re‑polish, leaving the surface visually flawless. Consistent quarrying and trained grading teams keep defect ratios low, giving fabricators predictable yield.
Pietra Grey’s cool graphite background and precise veining create a calm but luxurious aesthetic that suits both minimalist and classic schemes. The stone accepts a mirror polish above 85 gloss units, giving a deep, water‑like reflection, yet also responds well to honed, brushed or leathered finishes for softer light diffusion. Low porosity limits everyday staining, but its calcite base will still etch under acidic spills, so an impregnating sealer and pH‑neutral cleaners are recommended. Limited freeze–thaw cycling (≤ 25 cycles) in lab conditions showed no cracking, but long-term outdoor use in cold climates still requires edge drainage, periodic sealing and conservative design loads. Moreover, UV exposure may lighten the grey tone marginally over several years.
In polished form, the surface reflects light almost like black glass, while the bright whips of calcite veins provide crisp contrast without an overwhelming pattern. A honed finish drops the glare and makes the grey appear slightly lighter, whereas a brushed or leathered surface adds subtle depth, emphasising veins through micro‑shadowing.
Polished faces are ultrasmooth and cool to the touch, free from micro‑pitting thanks to resin back‑filling. Brushed finishes introduce gentle undulations that feel velvety rather than rugged. Leathered variants combine soft ridges with slight grip, making them popular for vanity tops that need tactile interest without catching dust.
Internal test data (50 cycles, ASTM C666) showed no cracking and no discernible colour loss after extended UV exposure. However, as with any calcitic marble, prolonged contact with acidic liquids such as lemon juice or wine can cause a dull spot. Prompt wiping and yearly resealing minimise visible etching in everyday use.
With more than ≈ 95 percent calcium carbonate, Pietra Grey reacts slowly to weak acids, releasing carbon dioxide and leaving a matte patch if unprotected. Modern solvent‑free penetrating sealers form an invisible barrier that resists acid for enough time to clean spills, while still allowing underlying stone to ‘breathe’ and equilibrate moisture.
Pietra Grey Marble comes in a broad catalogue of sizes to fit both bespoke and standard projects. Slabs cut on gang‑saws range from 240 to 320 centimetres long and 120 to 190 centimetres wide, in 20‑ or 30‑millimetre thicknesses that suit walls, counters or floors. Tile programs cover 30 × 30 cm up to 60 × 60 cm, all calibrated for precise installation. Outdoor projects can specify 30‑millimetre sand‑blasted pavers or French patterns, while manufacturers also supply mesh‑mounted mosaics, stair treads, skirting boards and 40‑millimetre worktops on demand.
Standard slabs of Lashtar Marble measure 260–290 cm in length and 120–190 cm in width, sawn at 2 or 3 cm thick. After kiln‑drying, technicians apply epoxy netting on the back to stabilise micro‑fissures, then calibrate thickness to within ±0.5 mm. These wide canvases enable book‑matched feature walls or monolithic islands with minimal joints.
Factories cut calibrated tiles from premium slabs, offering 30 × 30, 40 × 40, 60 × 30 and 60 × 60 cm modules at 10 or 12 mm thickness. Edges are precisely sawn and optionally chamfered to keep grout lines neat. Tight dimensional tolerance speeds installation and lets designers mix formats without lippage.
CNC machines mill vanity tops, stair treads, risers and wall panels to client drawings. Precision water‑jet cutting keeps curved profiles and sink openings crisp, with no thermal damage. Epoxy reinforcement and careful edge polishing permit slender cantilevers and complex geometric inlays in luxury hospitality or residential projects worldwide.
Mesh‑mounted sheets, usually 305 × 305 mm, come in herringbone, hexagon, chevron and penny‑round patterns. Each piece is water‑jet cut from vein‑matched stone, allowing installers to wrap shower niches or curved walls seamlessly. Neutral epoxy mesh keeps profiles flush while avoiding telegraphing, and sheets can be trimmed on site for perfect alignment.
Outdoor areas can specify 30 ‑ mm thick sand‑blasted or bush‑hammered pavers in 16 × 24, 24 × 36 cm or classic French pattern modules. However, It is recommended to use this stone grade only in regions with mild winters and install on a drained, frost-proof base. For heavy-traffic or severe-freeze zones, though, we suggest choosing a denser stone (e.g., granite).
Lashtar Marble factory‑finished boards commonly measure 100 × 10 cm at 15 mm thick, with a gently eased or pencil‑round top edge. Pieces are cut from the same slab batch as adjoining tiles, preserving colour uniformity. Taller custom profiles can be shaped for classical interiors that require deeper base mouldings.
Quarry output averages 12–18 tonnes per block, each cut in cubic geometry to maximise slab yield and simplify container loading. Homogeneous colouring lets exporters combine blocks from different benches without variation. A strategic reserve of about 360 000 tonnes (awaiting third-party geological survey confirmation) secures continuous supply during maintenance shutdowns or peak ordering seasons.
Thanks to its refined appearance and reliable strength, Pietra Grey Marble serves a wide range of architectural roles. Indoors it excels as large‑format floor tiles in hotel lobbies, sleek wall cladding in corporate foyers and waterfall countertops in high‑end kitchens. The stone’s balanced hardness accepts bathroom vanities and shower walls, provided surfaces are sealed against soaps. Outdoors, sand‑blasted pavers perform well on covered terraces in temperate zones, although heavy‑traffic driveways are better left to granite. Designers also book‑match slabs behind reception desks to create striking ‘butterfly’ vein features that become instant talking points.
FOB pricing for first‑quality Pietra Grey Marble slabs hovered between 30 and 65 US dollars per square metre in early 2025. Rates swing because block grade, slab dimension, finish and freight all push the final invoice. Global sea‑freight surcharges have recently added up to 8 dollars per square metre, especially on long‑haul routes, while spiking energy costs influence polishing expenses. As a result, developers planning hotel or mall projects often lock prices months in advance or reserve quarry blocks to shield budgets from volatility.
Premium A‑grade Lashtar Marble shows uniform graphite colour and uninterrupted parallel veins, so it commands the top of the price band. B‑grade may include stylolites or slight colour shifts, reducing cost but increasing fabrication time because installers must resin‑fill tiny pits and plan seam placement to disguise minor defects.
Large cubic blocks over three metres long yield more full‑size slabs with consistent veining, spreading fixed quarrying and transport costs across a greater surface area. Smaller or wedge‑shaped blocks raise off‑cut waste and shorten slab length, so producers lift the unit price to recover lost material.
Epoxy back‑netting, kiln drying, precision calibration and mirror polishing add labour, resin and power costs but sharply cut breakage and re‑work. Lines investing in multi‑head polishers achieve gloss above 85 units (60° geometry) and thickness tolerance within ±0.5 mm, whereas entry‑level plants accept wider variance, explaining lower ex‑works pricing for similar stone.
Polished or leathered surfaces demand finer diamond pads and longer machine cycles, usually adding eight to twelve percent over sawn‑cut slabs. Honed finishes fall in between. Heavy textures like bush‑hammering skip high‑gloss polishing yet require impact tools and sand‑blasting, making them roughly cost‑neutral instead of significantly cheaper.
A 40‑millimetre countertop or oversized panel weighs far more than a 20‑millimetre tile, increasing diamond blade wear, crane loads and container fuel costs. Greater mass uses extra raw stone and epoxy reinforcement, so producers price thicker, larger pieces proportionally higher to maintain margin while covering logistics.
Sea‑freight rates fluctuate with fuel prices and container shortages. When vessels stack up at Bandar Abbas, lead‑times stretch and exporters levy surcharges. Conversely, during low demand, freight discounts can offset rising energy costs. Seasonal quarry closures after heavy rain may also pinch supply and lift pricing temporarily.
Production starts with diamond‑wire saws tracing neat blocks from Lashtar’s steep faces. Chain saws carve working slots, and airbags gently tip freed masses onto padded mats to avoid cracks. Lashtar Marble blocks are resin‑injected, kiln‑dried, then fed through gang saws that slice forty‑millimetre louvres into slabs. After oven curing, multi‑head polishers raise gloss, and inspectors grade each piece before foam‑sheet wrapping, fumigated wooden crating and container loading bound for Bandar Abbas port. The entire route is tracked to reduce breakage and keep delivery times predictable.
Installers should lay Pietra Grey on a rigid, level substrate using a white, flexible cement adhesive to prevent shadowing and ensure colour consistency. A 2‑ to 3‑millimetre grout joint absorbs thermal expansion without edge chipping, and movement joints must follow building dilation lines. Once grout is dry, craftsmen wipe the surface clean and apply a solvent‑free impregnating sealer twice, ten minutes apart, removing excess before it skins. Resealing every twelve to eighteen months keeps porosity low and finishes looking fresh without changing the natural matte or gloss selected.
Common installation pitfalls stem from misunderstanding marble’s calcitic nature. Acid‑based cleaners, even mild vinegar sprays, dull the finish within minutes, so owners must use pH‑neutral products and wipe spills quickly. Outdoor use in freeze‑prone zones requires edge drainage and periodic resealing; otherwise trapped water may freeze and open small veins. Another risk is setting slabs on flexing wooden floors, which can transmit movement and crack corners. Using a decoupling membrane and allowing full adhesive cure eliminates most of these issues, extending the stone’s life for decades.
JAM Stone Co. positions itself as an integrated Supplier of Lashtar Marble by controlling every step from quarry bench to final inspection. Long‑standing partnerships with miners in the Lashtar region secure steady block access, while modern water‑jet cutters, CNC calibrators and multi‑head polishers in the Isfahan plant give the firm tight control over thickness, gloss and squareness. In‑house labs measure density and absorption each shift, releasing only batches that meet ISO 9001 metrics. This closed loop means architects receive consistent colour and vein harmony across multiple containers.
As a seasoned Exporter of Pietra Grey Marble, JAM Stone Co. runs multi‑stage inspections that check visual grading, flatness and edge integrity before crates leave the factory. Documentation covers ISO 14001 environment management and CE conformity, easing customs clearance in Europe and the GCC. The company fills orders from 200 to 10 000 square metres, offering project‑based cutting and matched slab sets. Dedicated logistics teams consolidate containers, optimise weight distribution and track shipments, keeping delivery windows predictable even during high‑season demand.
The Lashtar deposit that feeds JAM operations is an exclusive bed of uniform graphite tone, enabling the firm to act as a consistent Provider of Pietra Grey Marble. Reserves exceed three hundred and sixty thousand tonnes, with new benches opened in rotation to keep colour stable. Direct partnership lets engineers plan extraction for minimal waste and limited overburden. Water recycling systems, dust suppression sprays and progressive restoration programmes demonstrate a commitment to eco‑conscious extraction without compromising block quality or volume.
Finished slabs are interleaved with foam sheets, wrapped in moisture‑barrier film and positioned in fumigated pine crates fitted with corner protectors. Jam Stone Co. labels each crate with batch number, finish, thickness and destination project code to simplify on‑site sorting. Container layouts rely on 3‑D modelling to balance weight and reduce empty space, a practice that keeps in‑transit breakage below two percent and lowers freight cost per square metre. Tiles and cut‑to‑size pieces travel on heat‑treated pallets with shrink‑wrap to prevent surface scuffing.
also known as Lashtar Marble in Iran, is renowned worldwide for its stunning appearance. With its grayish-black background and distinctive white streaks, this marble has been a favorite among builders and designers for its elegance and versatility.
Pietra Gray Marble (Lashtar) has a significant presence in international markets, including the following countries: Bahrain, Kuwait, United Arab Emirates (UAE), Oman, Canada, Australia, Italy
These countries import Pietra Gray Marble for various construction and interior design projects, leveraging its unique characteristics and aesthetic appeal.
Address: No. 1014, JAM Center, Jamaran St., Niavaran, Tehran, Iran – 1977763988
Email: info@jamstoneco.com
