Product Overview

MSI XL RockMount® Alaska Gray 9" × 18" Splitface Marble Corner Panel creates a continuous stacked-stone transition around 90-degree outside corners. Each preassembled L-shaped piece measures 9" high with a 12" long return and 6" short return. The two returns combine to 18", which is why the product is also marketed as a 9" × 18" corner panel.

Crafted from genuine natural marble, Alaska Gray displays soft silver-gray, pale pewter and white tones with subtle natural veining. Its rugged splitface surface creates architectural depth and shifting shadows while coordinating directly with MSI Alaska Gray XL 9" × 24" flat ledger panels.

Technical Specifications

MSI confirms the marble composition, splitface finish, Low variation, grout-free installation, corner dimensions and item number. Packaging data confirms four corner pieces covering approximately 4.5 square feet per box.

Recommended Applications

• Fireplace Surrounds: Wraps projected fireplace walls and chimney breasts with continuous dimensional marble.

• Columns and Pillars: Finishes 90-degree outside corners without exposed saw-cut panel edges.

• Interior Feature Walls: Creates finished returns on living-room, foyer, hospitality and commercial accent walls.

• Outdoor Kitchens: Wraps barbecue islands, counters and entertainment structures with coordinating stacked stone.

• Exterior Cladding: Suitable for approved façades, entry columns and architectural projections with proper exterior detailing.

• Planter and Landscape Walls: Provides a decorative stone veneer over structurally sound masonry or concrete construction.

• Commercial Features: Suitable for reception desks, restaurant counters, hospitality columns and retail displays.

This is a nonstructural stone veneer. It should not be described as structural retaining-wall material.

Installation and Handling Guidelines

IMPORTANT: INSTALL CORNERS BEFORE FLAT PANELS

Establish the corner courses first, then cut and fit the coordinating Alaska Gray XL 9" × 24" flat panels between the corner returns.

• Alternate the Returns: Rotate successive pieces so the 12" and 6" returns alternate between adjoining walls. This prevents a continuous vertical seam.

• Approved Substrate: Install over structurally sound concrete, masonry, cementitious backer board or an approved exterior veneer substrate.

• 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 every corner panel. Exterior, wet-area and fireplace installations require substantially complete mortar coverage.

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

• Course Alignment: Maintain consistent 9-inch courses so the corners align with the coordinating 9" × 24" XL panels.

• Wall Flatness: Correct substrate irregularities before installation. Do not use excessive mortar thickness to compensate for uneven walls.

• Temporary Support: Use a properly secured ledger board when necessary to support the first course while the mortar cures.

• Exterior Installation: Include project-appropriate waterproofing, flashing, drainage, movement accommodation and freeze-thaw-rated setting materials.

• Fireplace Installation: Follow the fireplace manufacturer’s required clearances and applicable building codes. Natural marble alone does not make an improperly constructed assembly heat-safe.

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

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

Quantity Calculation

Each corner panel covers 9 vertical inches, or 0.75 linear foot, of one outside corner.

Divide the total vertical corner height by 0.75 and round up to the next whole piece. Then add approximately 10–15% for waste.

For multiple corners, calculate each vertical corner separately before adding the waste allowance.

Care and Maintenance

• Remove surface dust with 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 exterior, wet, grease-prone or stain-prone locations.

• Test enhancing sealers first because they may deepen the gray coloration.

• Do not direct high-pressure power washers closely at the stone or mortar joints.

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

Design Profile

• Aesthetic Inspiration: Contemporary lodge, organic modern, Scandinavian rustic and refined mountain design.

• Color Character: Soft silver gray, pale pewter and white with subtle natural marble veining.

• Visual Advantage: The L-shaped construction preserves the appearance of full-depth masonry around outside corners.

• Complementary Materials: White oak, walnut, concrete, blackened steel, limewash and warm plaster.

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

• Lighting Recommendation: Directional wall-wash or grazing light emphasizes the dimensional splitface texture.

Frequently Asked Questions

Is Alaska Gray XL marble or quartzite?

MSI identifies Alaska Gray XL as genuine natural marble. The existing “marble/quartzite” wording is incorrect.

Is the corner 9" × 18" or 9" × 12" × 6"?

Both descriptions refer to the same product. It is 9" high with a 12" long return and a 6" short return. The two returns total 18".

How many pieces are included in one box?

One box contains four L-shaped corner panels.

How much vertical corner does one box cover?

Four 9-inch-high pieces cover approximately three vertical linear feet of one corner.

Does this corner require grout?

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

Which flat panel coordinates with this corner?

It coordinates with MSI Alaska Gray XL 9" × 24" splitface marble ledger panel, item LPNLMALAGRY924.

Can it be installed outdoors?

Yes. MSI recommends Alaska Gray XL for exterior vertical applications. Proper waterproofing, flashing, drainage, mortar coverage and movement accommodation remain essential.

Can it be installed on floors?

No. MSI identifies this dimensional splitface product as a wall and veneer material rather than a walking surface.