Limestone, chalk, limescale and marble are chemically the same. They are all forms of calcium carbonate.
Think of calcium carbonate as being milk (calcium, Ca) on a car bonnet, along with items associated with calcium carbonate:
• Limes in the back of the car are singing scales (limescale)
• The wheels on the car are marbles (marble is formed from highly pressurised limestone)
• Chalk tyre marks on the road (chalk is mainly limestone)
• The car is swerving around a stone that looks like a lime segment (limestone)