Hi, not chlorine generally, this will generally be salts that form from the lap water / sitting water that is continually evaporating , these then layer on to each other - which further down the line will almost produce a crust. If yours have not gone to far you can try an alkaline product- we have lithofin power clean -( other avalible to deal with salt) use this diluted 1-2 with an white emulsifying pad .
Do not be tempted to use an acidic product or lime scale remover as this will remove your stone as quick as the scale.
If the salts have built to far , I generally will remove these easily with a diamond pad on a flex machine, a local restorer could do this for you. Once removed and fully dry re- impregnate with a suitable impregnator , we have mn stain stop - other brands available. If still a dry - dusty finish , you could use a colour enhancer to lift the colour. These will then keep dirt,salt and water marks above the stone and you will then maintain them at there earliest form -you will then be able to remove easily with the hand pads and poss a bit product when required.
This is not a bad product for around a pool, you just need the right info to maintain it. You're impregnator will reduce most porosity,
If you have photos we can see what stage of salt ingress you are at.