Brazilian black riven slate hearth, 1200x900x20mm, calibrated for standard installations. Natural riven surface passes the credit card levelness test with precision-sawn edges. Dispatched from Milton Keynes for UK delivery.

Brazilian Black Riven Slate Hearth Slab | 900×900×20mm

★ 4.81 · 468 reviews | In stock
Crack Guarantee ⓘ
If your slab cracks within 14 days of delivery (provided it is installed within that same 14-day window), we'll replace it completely free.
Free Photo Service ⓘ
Premium orders always include a photo of your exact slab before dispatch. Standard orders include it when a cutting or finishing service is added.
Guaranteed Level Surface ⓘ
Guaranteed flat riven texture — a standard credit card slides smoothly across the surface without catching.
STEP 1 · CHOOSE PURCHASE TYPE

FREE Shipping to England & Wales on all full-crate orders! Dispatched directly from our Colchester distribution centre Each crate contains 15 slabs. Are you in the trade? Sign in or apply now to unlock direct trade pricing, priority stock, and dedicated support

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STEP 2 · CHOOSE YOUR GRADE
All our grades share the exact same structural quality and durability. Grading is purely based on visual appearance and surface character.
Need help choosing? View Grade Guide →
STEP 3 · ADD A SERVICE (OPTIONAL)
📦 Standard Size | Full Slab Supplied as a complete factory slab—no cutting or post-finishing applied. Fast, direct dispatch
See how our Workshop preps your order →

Workshop services are available for single slab purchases only. For bulk crate processing, please contact our trade desk.

Quantity
Base Slab Price: £71.15 inc. VAT
£71.15 inc. VAT
Trade customer? Log in for exclusive trade pricing →
Not sure which stone is right? Order a sample first →
£71.15

Key Specifications

  • Dimensions: 900×900×20mm
  • Material: Brazilian Black Riven Slate
  • Primary use: Wood-burning stove hearths
  • Guarantee: 7-Day Crack Guarantee
  • Photo service: Free photo of your exact slab before dispatch
Overview

Supplied by Bluesky Stone, based in Milton Keynes, specialising in Brazilian slate and limestone hearths available in standard stock sizes or custom-cut for trade and residential installations across England and Wales.

Looking for the ultimate log burner hearth or fireplace hearth stone? Engineered from direct-from-quarry Brazilian stone, this calibrated 20mm hearth slab combines rugged safety with contemporary style. Featuring a flat, subtle riven surface and clean 90° machine-sawn edges, it can be fully tailored to your exact dimensions through our custom-cut slate hearth fabrication service. Browse our Natural Riven Slate Hearths range to explore more options.

Highlights & Key Features

  • Direct-from-Quarry Pricing: Brazilian slate sourced container-direct to avoid retail markups.
  • Free Delivery on all full crate orders to England and Wales.
  • 14-Day Crack Guarantee: If your slab cracks within 14 days of delivery (provided it is installed within that same 14-day window), we'll replace it completely free.
  • Free Pre-Dispatch Photo Service: Every premium-grade order includes a free dispatch photo of your exact slab sent straight to you before delivery. Standard-grade slabs also include this service whenever a custom cutting or finishing service is added.
  • Guaranteed Level Surface: A standard credit card slides smoothly across without catching on sharp ridges on the surface.
  • Order a sample: Choose up to 2 free samples for a flat £5 delivery fee. See the texture and quality in person before committing to a full slab. Order your sample
Product Overview & Suitability

Yes, this 20mm slate hearth is designed for heavy or wood-burning stoves and fireplaces.

  • Heat Resistance: These calibrated slabs are engineered to withstand the weight and heat of a log burner. Not suitable for direct flame.
  • Dimensions: 900 x 900 x 20mm (+/- 1mm) with clean, 90° machine-sawn edges for a precise, contemporary fit.
  • Weight: 45 kg per slab (1-person lift)
  • Surface Finish: Subtle Natural Riven surface
  • Edge Finish: Clean 90° machine-sawn
  • Colour Profile: In its raw state, the stone features a Graphite Grey to Black profile with natural variation. Once sealed, the stone transforms to a much deeper, darker tone.
  • Applications: Ideal for living rooms and dining rooms
Technical Specifications (Lab Results)

This slate has been rigorously tested to ensure it meets the highest safety and durability standards:

  • Slip Resistance: PTV 62 (Dry) / PTV 49 (Wet) – Rated as Low Slip Risk
  • Flexural Strength: 19.6 MPa (48 Freeze-Thaw Cycles)
  • Water Absorption: Less than 0.50% (High Frost Resistance)
Natural Riven Grading: Standard vs. Premium

We offer two distinct grades for this natural stone — part of our Slate Hearths range. Both share identical 20mm structural integrity and test results, but differ in visual selection.

  • Standard Grade: Celebrates the raw character of natural stone with visible variations in texture, tone and pattern.
  • Premium Grade: Hand-selected for aesthetic harmony; manually sorted to ensure a homogeneous appearance with a consistent colour tone across the surface.

See our guide to choosing between Standard and Premium slate grades, including our Credit Card Test for surface quality.

Guaranteed Level Surface — The Credit Card Test:
Regardless of grade, every slab must pass our internal surface tolerance test: a standard credit card must slide smoothly across the riven surface without catching or snagging on sharp ridges.

Bespoke Cutting & Fabrication Services

Tailored stone solutions for a perfect hearth installation

Our in-house fabrication team based in Milton Keynes provides professional tailoring for our entire range of Brazilian Slate and Limestone slabs. We offer three service tiers:

1. Professional Laser Guided Cutting

We provide precise laser-guided straight-line cutting to match your dimensions.

  • Shapes: Squares, rectangles and pentagons
  • T-Shape: We can supply 2pc T-Shape solutions - significantly easier to handle and reducing the risk of the stone cracking during transit and installation

2. Deep Clean & Seal Service

Bring out the true character and depth of your natural stone.

  • Process: Each slab is deep-cleaned and washed to remove quarry dust and reveal its natural riven character.
  • The Finish: We apply two coats of Stovax Dressing Oil. For Brazilian Slate, this transforms the raw graphite-grey profile into a deeper, darker, and more luxurious tone.

3. The "Signature Bundle" Package (Best Value)

Our most popular choice for a professional, "high-end" fireplace finish. This package includes everything in the cutting and sealing services, plus:

  • Dressed Edges: We manually ease the edges and hone the sides of your stone (a process we call "dressing").
  • The Look: This creates a smooth, chamfered edge that offers a truly wonderful, high-quality aesthetic for modern and traditional homes.
  • Exceptional value - dressing the stone is included at no additional cost within this bundle, representing exceptional value.

See how our slate cutting, finishing, and sealing services work, from laser-guided cuts to the Signature Bundle finish.

Local Service & Trade Support

Local to Milton Keynes?

  • Free Click & Collect to waive delivery fees entirely.
  • Trade-Ready service for local installers who require precision-cut material on short lead times. Contact our team for details.
  • Free Samples - collect samples totally free from our warehouse to check colour and texture.
Ordering & Delivery
  • Free Delivery: Applies to all full crates and covers all areas of England and Wales
  • Single slab(s): If you're in England or Wales, your delivery cost shows automatically at checkout — no quote needed. Delivering to Scotland, Northern Ireland or the Islands? Delivery costs vary by location, so we provide a free personalised quote instead.
  • Nationwide Logistics: Direct-to-site delivery via 3rd-party nationwide pallet delivery. Offloaded by pallet and delivered kerbside
  • Customer quotes: Call 01908 46 46 56 or email drawings to sales@blueskystone.com.
Frequently Asked Questions
What size hearth do I need for a wood-burning stove?
Your hearth must comply with Building Regulations Document J. As a guide it should extend at least 300mm in front of the stove door and 150mm either side. Our 900x900mm slab suits smaller stove installations. Always check your stove manufacturer guidelines.
What is the difference between Standard and Premium grade?
Both grades are the same Brazilian riven slate from the same quarry — the difference is appearance consistency, not structural quality. Standard has natural tonal variation and character. Premium is hand-selected for colour consistency and surface evenness. Both carry the same 7-day crack guarantee.
What is the Free Photo Service?
Before your slab leaves our Milton Keynes yard, we photograph it and send you the picture. You see exactly what is arriving before it leaves us — no surprises on delivery day. Included on all Premium grade orders and all Standard grade orders with a service added.
Does the slab come sealed?
No — supplied in its natural state. We recommend applying a stone oil or colour-enhancing sealer before installation. Our Signature Package includes professional edge honing and pre-sealing at our Milton Keynes workshop.
Can I have this cut to a specific size?
Yes — our cut-to-size service is available at checkout. Choose Standard (up to 14 working days) or Express (up to 7 working days, +£50). We cut rectangles, squares, two-piece configurations and pentagons. Complex bespoke shapes are referred to our specialist fabrication partner.
How is this slab delivered?
Single slabs are delivered by pallet to England and Wales for £78 inc. VAT. Full crates (15 slabs) are delivered free of charge. Scotland, Northern Ireland, and islands — please request a quote at checkout.
What does ‘riven’ mean, and how does it differ from honed or brushed slate?
Riven slate is split along its natural cleavage planes, leaving a subtly textured, non-uniform surface that retains the stone's authentic character. Honed slate is ground flat and smooth to a matte finish, removing all surface texture. Brushed slate sits between the two — wire-brushed to soften the riven texture without fully flattening it. Our slabs pass the Credit Card Test, meaning the riven surface is flat enough for practical use without sharp ridges that could catch underfoot or snag during cleaning.
How heavy is a 900×900×20mm slate slab, and does my floor or hearth base need reinforcing?
At 20mm calibrated thickness, these are substantial slabs. We recommend confirming your sub-floor load capacity with your installer before laying, particularly on suspended timber floors. For solid concrete or screed bases, no additional reinforcement is typically required. If you're unsure, contact our team with your floor construction details and we can advise.
How does Brazilian riven slate compare to granite or limestone as a hearth material?
Slate offers naturally low water absorption (≤ 0.50%) and strong flexural strength (19.6 MPa), making it highly resistant to thermal cycling and moisture — key for hearth use. Granite is harder and more scratch-resistant but typically more expensive and heavier to handle. Limestone is softer and more porous, requiring more frequent sealing and being more susceptible to acid etching from cleaning products. Slate's riven surface also provides inherent slip resistance (PTV 62 dry / 49 wet), which granite and polished limestone cannot match without additional surface treatment.
What other sizes does this come in?
This riven slate hearth is also available in 1200×900×20mm, 1500×900×20mm, 900×600×20mm, all in the same riven finish and 20mm thickness. (Automatically generated from current sizing — always up to date.)