Because of the way it was formed, granite is very strong, and resists water and food acids. It looks like a bunch of crystals packed together very tightly. Some granites have larger crystals, and some have very small crystals. Granite is an extremely common stone all over the world.
It is found on all seven continents and the presence of different minerals during its formation causes granite to take on an almost endless variety of colors, from white to black, red to blue, and every blend of color possible.
Marble is a metamorphic rock. It began its journey as a coral reef beneath an ancient sea millions of years ago. The reef eventually became buried under earth and rock, and the calcium-rich bones of the little creatures which lived in the reef became calcium carbonate, or limestone. Then, the limestone was buried even further beneath the earth’s surface, and, under heat and pressure, the calcium carbonate crystallized into marble.
Quartz is a hard crystalline mineral which is found abundantly all over the Earth in a variety of forms. It is the most common mineral on Earth, making up 12% of the Earth’s crust by volume, and is used in a wide variety of applications including jewelry, scientific research, manufacturing, and building. Because of its many uses, quartz is also a very important mineral, and some rare varieties are considered to be quite valuable. It can also be quite beautiful, especially when cut and polished by a jeweler who appreciates its properties. It is often used as a cheaper substitute for fancier gems, and when handled well, it can be difficult to distinguish from more expensive counterparts.
Quartzite is a metamorphic rock that has been formed from sandstone. A metamorphic rock is one that has been altered by energy that can include pressure and heat. Marble, for instance, is also a rock of this type that has been formed from limestone. Granite, on the other hand, is an igneous rock, which means that it has crystallized and solidified from lavas molten state.
Onyx is a semi-precious form of chalcedony which has alternating straight bands of color, most commonly brown, red, white, and black. Chalcedony is the group name for a large family of stones, all of which form from silicon dioxide, also known as quartz. In order to be classed as chalcedony, a stone must be milky, and translucent to transparent, often with layers or bands of color. The color of onyx, as with other forms of chalcedony, is created through impurities which seep into the rock as it forms.