Choosing Stone: Granite Unlimited Inc.

Granite Counters, Marble Vanities & More – Twin Cities MN

Natural stone can be classified into two general categories according to its composition: siliceous stone or calcareous stone. Knowing the difference is critical when selecting cleaning products (Click here for more information on Cleaning & Caring for your natural stone).

Siliceous Stone

Siliceous stone is comprised mainly of silica or quartz-like particles. It tends to be very durable and relatively easy to clean with mild acidic cleaning solutions.

Types of siliceous stone include:

  • Granite
  • Slate
  • Sandstone
  • Quartzite

Calcareous Stone

Calcareous stone is composed mainly of calcium carbonate, and is sensitive to acidic cleaning products and frequently requires different cleaning procedures than siliceous stone. What may work on siliceous stone may not be suitable on calcareous surfaces.

Types of calcareous stone include:

  • Marble
  • Travertine
  • Limestone
  • Onyx

How To Tell The Difference Between Siliceous & Calcareous Stone

A simple acid sensitivity test can be performed to determine whether a stone is calcareous or siliceous. To do the test, you will need about 4 oz. of a 10% solution of muriatic acid (CAUTION: Muriatic acid is corrosive and is considered to be a hazardous substance. Proper head and body protection is necessary when it is used) and an eye dropper, or you can use household vinegar and an eye dropper.

Because this test may permanently etch the stone, select an out of the way area, and be sure to test several inches away from the mortar joint. Apply a few drops of the solution to the stone surface on an area about the size of a quarter.

  • If the stone is calcareous, the acid drops will begin to bubble or fizz vigorously.
  • If little or no reaction occurs, the stone can be considered siliceous.

Thoroughly rinse the area with clean water and wipe dry. The test may not be effective if surface sealers or liquid polishes have been applied. If an old sealer is present, chip a small piece of stone away and apply the acid solution to the fractured surface.

Types of Natural Stone Finishes

Polished Finish

A polished finish has a glossy surface which reflects light and emphasizes the material’s color and marking. A polished finish is used on walls, furniture tops and other items.

Honed Finish

A honed finish is a satin-smooth surface with relatively little light reflection. Generally, a honed finish is preferred for areas where heavy traffic will wear off the polished finish. A honed finish may also be used on furniture tops and other surfaces.

Flamed Finish

A flamed finish is a rough textured surface used frequently on granite floor tiles.

Marble & Granite Colors and Appearance

Granites and marbles are quarried throughout the world in a variety of colors with varying mineral compositions. In most cases, marbles and granites can be recognized by visible particles at the stone’s surface. Marble will normally show “veins” or high concentrations. The minerals in granite will appear typically as small flecks uniformly distributed in the stone. Each stone is unique and will vary in color, texture and marking.


Sandstones vary widely in color due to different minerals and clays found in the stone. Sandstone is light gray to yellow or red. A dark, reddish brown sandstone, also called brownstone, has been commonly used in the northeastern United States and eastern Canada. Bluestone is a dense, hard, fine – grained sandstone of greenish – gray or bluish – gray and is quarried in the eastern United States.


Limestone is a widely used building stone with colors typically light gray, tan, or buff. A distinguishing characteristic of many limestones is the presence of fossils that are frequently visible in the stone surface.


Slate is dark green, black, gray, dark red or multi-colored. It is most commonly used as a flooring material and for roof tiles and is often distinguished by its distinct cleft texture.

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