Bluestone is dense, hard and a fine-grain sandstone. It is a bluish or greenish color. Try to avoid stains on the stone, using coasters on top of surfaces and barriers under furniture and other objects. Use a mild detergent to clean bluestone. For more persistent stains, determine what caused the spot first so you can clean it properly.
To avoid staining bluestone, use coasters under all glasses and avoid spills. Citrus juices, alcohol and other acidic foods may dull the surface. Don't put hot items directly on the stone. Use barriers under furniture to avoid scratches on floors. Place floor mats or rugs near entrances to lessen the amount of sand and dirt that can scratch stone. If you spill something, blot it right away. Don't wipe it up. Use plain water on the area with mild soap. Dry it with a soft cloth.
Use a neutral cleaner, stone soap or a mild liquid detergent and warm water to clean bluestone. On floors, use a rag mop. Use a soft cloth on other surfaces. Rinse the surfaces thoroughly and change the water often. Don't use scouring creams or powders. Don't use vacuum cleaners, as they may scratch the surface.
If you still have stains after cleaning your bluestone, try to figure out what caused the stain. Organic stains often cause a pinkish-brown color from coffee, fruit or leaves. These stains sometimes vanish after the source is removed. For outdoor bluestone, the sun and rain will normally bleach out any stains. For indoor cleaning, use a 12-percent hydrogen peroxide solution and a few drops of ammonia. Oil-based stains usually make the stone darker. Clean this gently with a soft, liquid cleanser.
For ink stains, try bleach or hydrogen peroxide on light-colored stone. On darker stone, try lacquer thinner or acetone. Water spots, surface scratches and nicks can be buffed off with dry, 0000-size steel wool. On biological stains such as mildew or algae, use a half-cup of ammonia, bleach or hydrogen peroxide diluted in water. Don't mix these chemicals together. Choose one.
If you have small spots of paint on bluestone, use a lacquer thinner to remove. You can also try scraping the spots off with a razor blade. For heavy paint stains, use a commercial paint stripper.
If the stains are from metal, such as rust or iron, you'll need to remove them with a poultice. These stains, from nails, plant pots or metal furniture, are difficult to remove and may be permanent.