Sedimentary rocks such as limestone or shale are hardened sediment with sandy or clay like layers strata they are usually brown to gray in color and may have fossils and water or wind marks.
Rocks with white crystals inside.
Collect several rock samples with crystals before identifying them.
Many excellent books and websites have been written to help identify crystals on or within rocks.
Crystals with small flat surfaces are said to have facets all crystals have a faceted surface but not all crystals have multiple facets.
If no crystals form the result will be natural glass.
Igneous rocks such as granite or lava are tough frozen melts with little texture or layering rocks like these contain mostly black white and or gray minerals.
It was once believed that rock crystals were ice too frozen to melt.
Typically the inclusion of clay gives jasper a yellowish white to gray tone.
It is most often black gray or white and often has a baked appearance.
Dalmatian jasper a fine grained dense quartz called chalcedony jasper is found in a variety of colors.
Shells tree branches roots and other organic materials often decay away to leave a void for the formation of mineral materials.
Finding a cool looking rock and then dissolving the calcite out of it with white vinegar to expose crystals in one week.