The Ultimate Guide to Crystals & Stones: A Practical Path to Personal Power, Self-Development, and Healing - Uma Silbey 2016

Physical Description of Rocks
Basic Crystal and Stone Information

As explained earlier, in order to do the most effective work with crystals and stones, it is helpful to know about rocks in general. We should learn how they are made, because the forces that caused them are still stored within the stones, which, in turn, can affect us and our work with them. This is likely to be true whether we are aware of this influence or not. However, if we are aware of all of the stored forces within our stones, we can use these energies when we work with our stones.

Rocks and stones are two terms that are more often than not used somewhat interchangeably, although there is a difference between the two. Generally speaking, though made up of the same materials, a rock is larger while a stone is smaller. A rock is a large, rugged mass of hard mineral found above and below ground. It is immoveable. A stone, consisting of the same material, is smaller and moveable. A stone can be thrown easily, for example, while a rock cannot. Another way of understanding it is that rocks are made of smaller stones and stones are made from rocks. As a fragment of rock, stone is larger than sand, silt, or clay, roughly the size of gravel, pebbles, or as large as boulders. Sometimes it is thought that such differentiation is only a matter of language, the term “rock” originating from the Romance languages, while the term “stone” is of Germanic origin.

Nonetheless, a rock or stone is a naturally occurring mixture of minerals or other organic compounds. Quartz and feldspars, for example, are minerals, but when they form together, they become granite, a rock. Because rocks are a mixture of minerals and other compounds, they have no one specific chemical composition. Rocks, in general, are found in three types: sedimentary, igneous, and metamorphic, though there may exist many intermediary steps between these three main divisions. The differences between each type have to do with how they are formed.

You can often see the fossils, stones, pebbles, or sand that combined to create a sedimentary rock like this conglomerate rock with red jasper.

Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of material, together called sediment. Over time, the sediments accumulate in layers that eventually harden into rock. Generally, this rock is so soft that it is easily broken apart or crumbled. Often you can see the pebbles, fossils, stones, or sand in the rock. Limestone is a good example of this type of rock, as well as conglomerate, sandstone, shale, and dolomite.

When lava cools quickly, it will create rock that has a glasslike, shiny appearance. This fresh lava from the big island of Hawaii is cooling to form igneous rock.

Igneous rocks are formed when the molten rock within the earth cools and hardens. When this process happens within the earth (called intrusive), the rock crystalizing below the surface cools slowly, often allowing large crystals to form. Examples of intrusive igneous rocks are diorite, granite, pegmatite or peridotite. When this cooling and hardening process happens when magma reaches the earth’s surface, usually through volcanic eruption, the igneous rock is called extrusive. Lava, forming upon the eruption of magma, cools quickly. It then creates rock that has a glasslike, shiny appearance without the formation of crystals. Sometimes, however, gas bubbles become trapped in the rock during the process of cooling, resulting in tiny holes and spaces in the rock. Basalt, rhyolite, andesite, and obsidian are examples of this type of rock.

Metamorphic rocks are formed under the surface of the earth from the changes that occur due to intense heat and pressure, usually squeezing. Resulting from these processes, some, though not all, of these rocks have ribbon-like layers in them that look like straight or wavy stripes of different colors. Metamorphic rocks may also contain various kinds of crystals, resembling shiny mirrors that are formed by minerals growing slowly over time on their surface. Good examples of this type of rock are marble, gneiss, slate, schist, or quartzite.

Metamorphic rocks may have ribbon-like layers in them that look like straight or wavy stripes of different colors. This metamorphic green quartzite is paired with a fossilized igneous rock.