Ardósia de Valongo – Dark Bluish Gray to Black Slate from Santa Baía, Valongo, Porto, PortugalArdósia de Valongo is a premium-quality natural slate quarried in Santa Baía, Valongo, Porto, Portugal. Known for its dark bluish-gray to black color, this slate features a fine, uniform texture with a slightly riven natural surface that enhances its visual depth and elegance. Due to its high density, low water absorption, and excellent mechanical strength, it is widely used in architectural, interior, and exterior applications.

1. Description & Appearance

Color & Pattern

• Base Color: Dark bluish-gray to black
• Texture: Fine-grained with a smooth, slightly riven natural surface
• Pattern: Uniform with minimal veining or speckling, offering a sleek and sophisticated look
• Variations: Some slabs may exhibit subtle linear or cloud-like patterns, enhancing their natural appeal

2. Technical Specifications

Physical & Mechanical Properties

• Water Absorption...0.45%
• Density...2809 kg/m³
• Flexural Strength...57.0 - 58.2 MPa
• Compressive Strength...49.4 - 65.6 MPa

Low porosity and high density make this slate highly resistant to water, weathering, and external damage.

High flexural and compressive strength ensures durability, even under heavy loads.

3. Chemical Composition (% by Weight)

• Silica (SiO₂)...50-60%
• Alumina (Al₂O₃)...15-25%
• Iron Oxide (Fe₂O₃)...5-10%
• Calcium Oxide (CaO)...1-3%
• Magnesium Oxide (MgO)...1-3%
• Carbon Content...Traces

Silica and Alumina dominance makes the slate highly durable and weather-resistant.

Low calcium and magnesium content ensures better acid resistance, making it ideal for both indoor and outdoor use.

4. Applications & Usage

Due to its durability and aesthetic appeal, Ardósia de Valongo is widely used in:

Interior Applications

• Flooring (residential & commercial)
• Wall Cladding (feature walls, fireplaces)
• Kitchen Countertops & Backsplashes
• Bathroom Vanities & Shower Walls
• Staircases & Steps

Exterior Applications

• Roofing Slate (weather-resistant and durable)
• Paving & Driveways (due to its high load resistance)
• Garden & Landscaping Features
• Facade Cladding & Ventilated Facades

Specialty Uses

• Tabletops & Furniture (dining tables, worktops)
• Memorials & Tombstones
• Engraving & Custom Signage

5. Cutting Sizes (cm) & Thickness Options

Ardósia de Valongo is available in various standard and custom sizes:

Slabs

Standard Slab Sizes:

• 200 cm x 100 cm
• 180 cm x 90 cm
• 120 cm x 60 cm

Thickness Options:

• 1 cm (for lightweight applications)
• 2 cm (most common for flooring & countertops)
• 3 cm (heavy-duty applications)

Tiles & Custom Cuts

30 x 30 cm, 40 x 40 cm, 60 x 30 cm, 60 x 60 cm

Custom cut-to-size pieces available for specific projects

6. Surface Finish Options

Ardósia de Valongo is available in a range of finishes to suit different design and functional needs:

• Natural Split (Riven Finish) → Textured, non-slip surface, ideal for roofing, paving, and wall cladding
• Honed Finish → Smooth, matte, and refined for modern interiors
• Polished Finish → Glossy and elegant, suitable for countertops and luxury applications
• Brushed Finish → A soft, worn texture that enhances the natural feel of the slate
• Flamed Finish → Rough, non-slip surface, ideal for exterior walkways

7. Maintenance & Care

• Sealing: Recommended for flooring and countertops to prevent staining
• Cleaning: Use pH-neutral stone cleaners; avoid acidic substances (lemon, vinegar)
• Scratch Resistance: High resistance, but avoid using sharp objects directly on polished finishes
• Water & Weather Resistance: Naturally waterproof, suitable for outdoor use