Robinson Flagstones Architect’s Corner
The Preferred Supplier of Pennsylvania Bluestone Since 1919
Since 1919 Robinson Flagstone has been the preferred supplier of Pennsylvania flagstone (Bluestone) servicing the needs of architects, landscape architects, designers and the construction industry in general. Our full cooperation is given for each job whether that requires technical information, budgeting, samples, or design concepts.
Our years of accumulated knowledge and continued research is complimented by our fully trained staff in sales, design and drafting, right down to the actual craftsmen who cut each individual stone. We are constantly studying and experimenting with our products to secure architectural effects for residential, institutional and commercial applications. Specify us by name for full cooperation and quality controlled source.
Shop drawings are provided with most jobs so review of the design is available prior to any fabrication.
Robinson Flagstone is a specially selected Pennsylvania bluestone (not slate). The stone itself is only quarried in a small region of Pennsylvania and lower state New York formed during the Devonian age. Bluestone is composed of fine grained silica sand cemented together by very strong binder materials. Fossilized sediments plus minerals present during formation contributed to the various shades of blue, gray, green, lilac and the combination of these tones. With a natural cleft surface texture, the stone has slight variations which while true to one plane offer a relatively smooth surface without the annoyance of an overly rough stone. This material is one of the toughest known stones to abrasion (approximately seventy percent quartzite) making it virtually non-slip whether wet or dry. The stone is very resilient and stable, resisting cracking and disintegration
PENNSYLVANIA BLUESTONE ASTM QUALIFICATIONS
ASTM C 616: CLASSIFICATION OF SANDSTONE–TYPE II QUARTZITE SANDSTONE
| Silicon Dioxide – 72.8% | Iron Oxide (Ferrous) – 2.50% |
| Aluminum Oxide – 12.2% | Magnesium Oxide – 1.20% |
| Iron Oxide (Ferric) – 1.92% | Sodum Oxide – .85% |
| Calcium Oxide (Lime) – .70% | Titanium Oxide – 1.16% |
Acid Resistance: N/A
Edge Detail: Sawn, Thermal (flamed), Rocked, Rubbed, Bullnosed, ½” Radius, ¾” Radius, DuPont, Cove DuPont (Please note that these edge details are only applicable to thermal bluestone, not natural cleft)
Texture: Thermal, Natural Cleft
Thickness Range: 3/8” to 30” thick
Lippage/Warpage: Quality Controlled
Flaking: Quality Controlled
Sealer Recommendation: N/A
Percentage Breakage: Quality Controlled
Approximate Crate Size: 42” x 48” pallet, Approximately 3,600 lbs.
Recommended Areas of Usage: Interior or Exterior
Peculiar Characteristics: Only quarried in Northeast Pennsylvania and Southern New York
ASTM QUALIFICATIONS OF SANDSTONE
| SAMPLE ID | ABSORPTION | SPECIFIC GRAVITY |
|---|---|---|
| #1 | 1.09% | 2.810 (162.86 pcf) |
| #2 | 1.04% | 2.607 (162.68 pcf) |
| #3 | 1.11% | 2.608 (162.74 pcf) |
| Average | 1.08% | 2.608 (162.74 pcf) |
| SAMPLE ID | PARALLEL TO BED | PERPENDICULAR TO BED |
|---|---|---|
| #1 | 2093 psi | 2901 psi |
| #2 | 2268 psi | 2842 psi |
| #3 | 2188 psi | 2755 psi |
| #4 | 2209 psi | 2951 psi |
| #5 | 2213 psi | 2832 psi |
| Average | 2194 psi | 2856 psi |
| SAMPLE ID | PARALLEL TO BED | PERPENDICULAR TO BED |
|---|---|---|
| #1 | 14235 psi | 18523 psi |
| #2 | 13960 psi | 18910 psi |
| #3 | 14891 psi | 18546 psi |
| #4 | 15124 psi | 17953 psi |
| #5 | 14200 psi | 17997 psi |
| Average | 14482 psi | 18386 psi |
| SAMPLE ID | PARALLEL TO BED | PERPENDICULAR TO BED |
| #1 | 13120 psi | 17424 psi |
| #2 | 12900 psi | 17019 psi |
| #3 | 13006 psi | 16841 psi |
| #4 | 12854 psi | 16420 psi |
| #5 | 12910 psi | 17283 psi |
| Average | 12958 psi | 16988 psi |
| SAMPLE ID | THERMAL FACE | NATURAL CLEFT |
|---|---|---|
| #1 | 26.8 | 9.2 |
| #2 | 27.4 | 8.8 |
| #3 | 26.9 | 8.6 |
| Average | 27.0 | 8.9 |