Our company sells cobble stones mainly in 4 colors, black (basalt & granite), dark grey, light grey granite and porphyry. Sizes used are mainly 10x10x4-6 cm. and thicker size 6-8 cm. The latter is used when trucks and/or buses are using the road surface.
Other, larger sizes are also available, including sleepers of 50 or 75 cm x 15/15 cm. Normally cobble stones are placed directly on prepared stabilized sand substratum. They also may be installed on a concrete basis. As subsidence is common in many areas, the 1st method allows break-up every 5-8 year to raise the level, without incurring high costs. Environmentally it’s also better as no concrete needs to be removed and dumped elsewhere. Cobble stones, need like all road surfaces proper draining in the sub-soil. Basalt Cobblestone are self cleaning in full sunlight. Lighter granite cobblestone are less resistant to outside polluting elements.