MSI RockMount Glacial Black 6" × 18" Marble Corner Panel

Product Overview

MSI RockMount® Glacial Black 6" × 18" Splitface Marble Corner Ledger Panel provides a finished 90-degree transition for Glacial Black stacked-stone installations. Each preassembled L-shaped corner measures approximately 6" high with 12" and 6" returns, allowing the textured stone pattern to wrap naturally around columns, fireplace surrounds, exterior façades, and outdoor kitchen structures.

Crafted from genuine natural marble, Glacial Black combines deep charcoal and soft black tones with contrasting white and pale-gray veining. Its rugged splitface surface produces substantial depth and dramatic shadow, coordinating directly with MSI’s Glacial Black 6" × 24" flat ledger panels.

Recommended Applications

• Fireplace Surround Corners: Creates a continuous stacked-stone appearance around fireplace projections, chimney breasts, and framed feature walls.

• Column and Pillar Wraps: Finishes 90-degree outside corners without exposing flat saw-cut panel edges.

• Outdoor Kitchen Islands: Wraps barbecue islands, counters, and entertainment structures with dimensional charcoal marble.

• Exterior Façades: Suitable for entry columns, architectural projections, accent walls, and other approved exterior veneer installations.

• Shower and Tub Surrounds: MSI lists Glacial Black for shower and tub walls when installed over a complete waterproofing system.

• Commercial Features: Adds a refined dark-stone finish to restaurant counters, hospitality columns, lobby walls, and retail displays.

Design Profile

• Aesthetic Inspiration: Dark luxury, modern lodge, urban industrial, contemporary rustic, and mountain modern.

• Color Character: Deep charcoal and black with soft white and pale-gray natural marble veining.

• Visual Advantage: The L-shaped format maintains the illusion of continuous stacked masonry around outside corners.

• Complementary Materials: Dark walnut, natural oak, blackened steel, concrete, leather, and warm plaster.

• Complementary Metals: Matte black, aged bronze, gunmetal, and brushed stainless steel.

• Lighting Recommendation: Grazing light from above or below accentuates the splitface texture and marble veining.

Technical Specifications

MSI confirms the product as splitface natural marble with medium variation, grout-free construction, and matching flat panels. Official MSI product page

Installation and Handling Guidelines

⚠️ IMPORTANT: INSTALL CORNERS BEFORE FLAT PANELS

Establish the corner courses first, then cut and fit the coordinating 6" × 24" flat panels into the corner returns.

• Alternate Corner Direction: Rotate successive corner pieces so the 12" and 6" returns alternate between walls. This prevents a continuous vertical seam and produces a more natural masonry appearance.

• Approved Substrate: Install over structurally sound concrete, masonry, or properly secured cementitious backer board. Painted drywall is not appropriate for heavy, wet, exterior, or high-heat installations.

• Mortar Selection: Use a polymer-modified Large and Heavy Tile mortar meeting ANSI A118.4 or A118.15 and approved for natural marble.

• Mortar Coverage: Directionally trowel the substrate and back-butter each corner panel. Exterior, fireplace, and wet-area installations require substantially complete mortar coverage.

• Grout-Free Installation: Butt panels tightly together without conventional grout joints. Remove exposed mortar before it cures.

• Course Alignment: Maintain consistent 6" courses so the corners align with coordinating Glacial Black flat panels.

• Wall Flatness: Correct substrate irregularities before installation. Do not compensate for uneven walls with excessively thick mortar.

• Exterior Detailing: Provide appropriate flashing, drainage, waterproofing, movement joints, and freeze-thaw-rated setting materials.

• Fireplace Clearance: The complete assembly must comply with fireplace-manufacturer clearances and local building codes. Natural marble alone does not make an improperly constructed wall assembly heat-safe.

• Cutting Safety: Wet-cut with a suitable diamond blade. Never dry-cut or grind because marble fabrication produces respirable crystalline-silica dust.

• Order Allowance: Add approximately 10–15% for breakage, cuts, shade blending, and future repairs.

Quantity Calculation

Each corner panel covers 6 vertical inches, so two pieces are required for every vertical foot of corner.

For multiple corners, calculate each vertical corner separately and then add approximately 10–15%.

Care and Maintenance

• Remove dust using a soft-bristle brush or vacuum attachment.

• Clean with warm water and a neutral-pH natural-stone cleaner.

• Avoid vinegar, acidic cleaners, bleach, abrasive chemicals, and wire brushes.

• A penetrating natural-stone sealer may be applied in wet, exterior, grease-prone, or stain-prone locations.

• Test enhancing sealers first because they can noticeably deepen the charcoal coloration.

• Inspect exterior installations periodically for open joints, failed flashing, or moisture intrusion.

Frequently Asked Questions

Is this corner 6" × 18" or 6" × 12" × 6"?

Both descriptions refer to the same product. It is 6" high with a 12" long return and a 6" short return. The combined returns equal 18", which is why MSI calls it a 6" × 18" corner panel.

How many pieces are included in one box?

One box contains six corner panels.

How much does one box cover?

Six pieces cover approximately 4.5 sq. ft. of surface area or 3 vertical linear feet of one corner.

Does this product require grout?

No. RockMount ledger panels are designed for tight, grout-free installation.

What flat panel coordinates with this corner?

It coordinates with MSI Glacial Black 6" × 24" Splitface Ledger Panel, item number LPNLMGLABLK624.

Is Glacial Black slate?

No. MSI identifies Glacial Black as genuine natural marble.

Can it be installed outdoors?

Yes, when installed using an approved exterior veneer system with proper waterproofing, flashing, drainage, mortar coverage, and movement accommodation.