Product Overview
MSI Cosmic White 6" x 18" Stacked Stone Corner Panel is an L-shaped pre-assembled natural marble corner piece designed specifically to accompany the Cosmic White 6" x 24" Flat Ledger Panels from MSI’s Rockmount™ Collection. Engineered for outside 90-degree corners, this specialty piece features an L-shaped interlocking format that wraps seamlessly around structural edges, fireplace breasts, and exterior columns without exposing cut stone edges or requiring manual 45-degree miter cuts on-site.
Featuring the signature Cosmic White aesthetics, each panel showcases a split-face natural marble body with crisp white tones, subtle cream undertones, and light-reflecting quartz sparkles.
Technical Specifications
| Technical Property |
Value / Specification |
Standard / Compliance |
| Manufacturer / Brand |
MSI Surfaces (MSI) |
Rockmount™ Stacked Stone Collection |
| Color Name / SKU |
Cosmic White Corner (LPNLMCOSWHI618COR) |
Split-Face Natural Marble |
| Panel Format / Profile |
L-Shaped Corner (6" Height x 12" Long Arm / 6" Short Arm) |
Pre-Assembled 90° Corner |
| Thickness |
0.75" to 1.25" (~19 mm to 32 mm Variable Depth) |
Dimensional Ledger Profile |
| Surface Finish |
Split-Face / Split-Stone (Raw Textured Surface) |
Natural Rough Face |
| Material Type |
100% Authentic Natural Marble |
Natural Metamorphic Stone |
| Water Absorption |
Low (Varies by natural stone density) |
ASTM C97 |
| Frost Resistance |
Freeze-Thaw Resistant (Properly Sealed) |
ASTM C1026 |
| Grout Requirement |
Groutless Installation (Dry-Stacked Look) |
Butt-Joint Interlocking Corner |
| Applications |
Outside Fireplace Corners, Exterior Columns, Retaining Wall Corners, Bar Edges |
Interior & Exterior Vertical Walls ONLY |
Recommended Applications
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Fireplace Surrounds & Chimney Breasts: Wraps smoothly around outside 90-degree corners of fireplaces and mantels for a continuous stone slab look.
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Exterior Architecture & Hardscapes: Exterior wall corners, patio pillars, retaining wall ends, and outdoor kitchen islands.
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Interior Architectural Features: Bar corners, accent wall wraps, and reception desk returns.
Installation & Handling Guidelines
⚠️ CRITICAL WARNING: CORNER INSTALLATION PROTOCOL
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Install Corners First: When cladding walls with outside 90-degree angles, always set the 6x18 corner pieces first, working from the bottom corner upward. Once corners are set, interlock the standard 6x24 flat ledger panels outward across the remaining wall space.
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Alternating Corner Orientation: Rotate the L-shaped corner panels 180 degrees with each progressive row (alternating long-side-left and long-side-right) to stagger vertical joint seams down the corner edge.
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Mortar Selection & Color: Set corner panels using an ANSI A118.4 / A118.15 polymer-modified Large & Heavy Tile (LFT) thinset. Always use pure white thinset mortar to prevent dark mortar lines along white marble edges.
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Groutless Dry-Stack System: Corner pieces fit tightly butt-jointed against adjacent flat panels. Do NOT apply grout into the textured split-face surface.
Professional Recommendations
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Substrate Preparation: Ensure corner substrates (backer board, cement block, or concrete wall) are plumb, 90 degrees square, and structurally capable of supporting 8 to 11 lbs per square foot.
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Sealing Strategy: Protect against outdoor weathering, dust, and moisture by applying a premium solvent-based penetrating natural stone sealer (such as Miracle Sealants 511 Impregnator or StoneTech® BulletProof®) after full installation cure.
Care & Maintenance
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Routine Cleaning: Dust lightly with a soft brush or vacuum attachment. Clean dirt or surface marks using warm water and a pH-neutral stone cleaner.
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Avoid Acidic Cleaners: Never use vinegar, bleach, acidic chemical cleaners, or high-pressure power washers at close range on natural marble.
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Resealing Schedule: Reapply a penetrating stone sealer every 2 to 3 years on exterior corners or high-touch interior surfaces.
Design Profile
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Aesthetic Integration: Color and texture matched to pair perfectly with MSI's 6" x 24" Cosmic White Flat Ledger Panels.
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Architectural Finish: Eliminates unsightly open cut edges, exposed tile sides, or tedious hand-mitering on job sites.
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Lighting Interaction: Multi-depth split-face texture catches ambient side-lighting and spotlighting across 90-degree corner boundaries.
Frequently Asked Questions
Why should I buy 6x18 corner pieces instead of mitering 6x24 flat panels?
Pre-assembled L-corner pieces save significant labor time on site and create a factory-finished 90-degree transition. Hand-mitering split-face stone with variable thickness is extremely difficult and often results in chipped, uneven edges along outside corners.
How do the corner pieces interlock with 6x24 flat panels?
The ends of the 6x18 corner panels feature the same Z-shaped interlocking fingers as the 6x24 flat panels, allowing flat panels to slide directly into the corner piece without visible joint breaks.
Do corner pieces require grouting?
No. Just like the flat ledger panels, corner pieces are designed for a groutless, dry-stacked look.
