How to Group Exterior Stone

Separate stones by type, if you have collected stones from nature. If you have quartz, granite and limestone, for instance, separate each type into its own group. Skip this step if your project calls for mixing various types of stone or if your stones are of only one type.

Group stones by size and shape. If your project calls for stones roughly the size of bricks, for example, make a pile of stones that size. If you are working on an outdoor project using gravel-size stones, it may be easier to remove the larger stones than to pick out the smaller ones from the pile. For a walkway, you may want rounder, flat-surfaced stones, while a retaining wall might look better with rectangular stones the size of bricks or concrete blocks.

Pile the stones according to color, smoothness or surface. Stone colors range from white to blue, red, pink, yellow, black, gray or green. Stones may be solid-colored, swirled or speckled. Some stones are smooth and some have jagged or rough faces. Stack stones together based on the types of faces you need. Keep in mind what type of adhesive, if any, you will use between the stones when you build your project.

Remove stones that are not hard enough or are too hard for your project. Stones are rated on the Measurement of Hardness Scale from 1 to 10. Marble is rated as a 3, while feldspar granite is a 6. Quartz granite is one of the hardest, with a MOH rating of 7 (diamonds rate 10). If the stones are for a patio floor, group the hardest stones together, since these will resist scratches and corrosion better than softer types.