Stone types and anchoring

One-line orientation

Stone selection is mostly a geology question — igneous / sedimentary / metamorphic sets hardness, porosity, and weather resistance — and the exam’s favorite trap is that marble is just metamorphosed limestone, so it is far softer and more acid-sensitive than granite.

Key points

• Igneous (crystallized molten rock): durable, hard, long-lasting.
  • Granite — hard, non-porous, scratch- and heat-resistant. Countertops, flooring, exterior applications.
• Sedimentary (deposited sediments): often porous and acid-sensitive.
  • Limestone — calcite, textured, porous and weaker than granite. Exterior facades, interior walls, low-traffic flooring.
• Engineered quartz is a manufactured surfacing product, not a natural stone class. It is non-porous and durable for kitchen/bath countertops, but keep it separate from igneous / sedimentary / metamorphic stone categories.
• Metamorphic (altered by heat and pressure):
  • Marble — derived from limestone; polished look but softer and more porous than granite, and acid-/weather-sensitive. Best for interiors (flooring, cladding, counters).
  • Slate — fine-grained, durable, slip-resistant. Roofing, flooring, landscaping.
• Shape / coursing:
  • Dimension (cut) stone — large finished slabs.
  • Ashlar — small squared/rectangular units; laid random or coursed.
  • Rubble — rough, uncut stone; laid random or coursed.
• Anchoring & use: a stone’s modulus of rupture governs how securely it holds metal anchors. Stone is typically a veneer held back to the structure with anchors/ties; the common types are strap anchors, Z-ties, three-layer truss ties, and ladder-loop ties, with heavy units lifted via Lewis pins / box pins.

Stone by rock class — and marble is just metamorphosed limestone

Geology sets durability: igneous granite is the hard, non-porous, exterior-grade stone.

View diagram Hide diagram 3 panels

3 panels side by side — swipe to compare →

Engineered quartz = manufactured surfacing, not a natural rock class. Sedimentary limestone and metamorphic marble trend softer and acid-sensitive.

Confusions / comparison

Stone	Rock class	Hardness / porosity	Weather / acid	Typical use
Granite	Igneous	Hard, non-porous	Resistant	Exterior, flooring, counters
Limestone	Sedimentary	Softer, porous	Sensitive (calcite)	Facades, interior walls, low-traffic floors
Marble	Metamorphic (from limestone)	Softer, more porous than granite	Acid/weather-sensitive	Interior cladding, flooring, counters
Slate	Metamorphic	Fine-grained, durable	Good; slip-resistant	Roofing, flooring, landscaping
Engineered quartz	Manufactured	Non-porous, durable	Good indoors	Kitchen/bath countertops

Related

→ CMU & grout (this topic): the other masonry material family · Mortar types: M, S, N, O, K (this topic): the bedding material common to stone and unit masonry · Brick types & grades (this topic): fired-clay units alongside natural stone.