Granite is an intrusive igneous rock composed of mostly two minerals: quartz and feldspar. An intrusive rock is crystallized from magma that cooled far below the Earth’s surface. Marble is a metamorphic rock that may be foliated or non-foliated, composed of recrystallized carbonate minerals. Most commonly calcite or dolomite. Both types are 100% natural. Granite is harder than marble and therefore harder to polish (it takes longer labor hours) and marble is softer, allowing for easier polishing and fabricating but more delicate when handling. Granite is more resistant to etching than marble.   Both are natural stone that need to be sealed to prevent staining. Cleaning is about the same, soap and water, Pledge multi-surface, liquid oxy-clean and non-ammonia based products and ph-balanced cleaners are fine.