Extrusive rocks form from volcanic eruptions above or at the Earth’s surface, and intrusive rocks cool and harden under the Earth’s surface. Generally, extrusive rocks have smaller crystals than intrusive rocks because they cooled faster and therefore gave the crystals less time to form.

Igneous rocks are formed from the solidification of molten rock material. Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass. These rocks include: andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff.

Extrusive igneous rocks come from lava, forming at the surface of the Earth and cooling quickly, meaning they form very small crystals. Intrusive igneous rocks come from magma, forming deep underground and taking longer to cool, meaning they form larger crystals.

Examples of extrusive igneous rocks are basalt, andesite, rhyolite, dacite, obsidian, pumice and scoria. Komatiite, a rare extrusive igneous rock, required much hotter melting temperatures to form than occur now.

Obsidian can be used to make extremely sharp knives, and obsidian blades are a type of glass knife made using naturally occurring obsidian instead of manufactured glass. Obsidian is used by some surgeons for scalpel blades, although this is not approved by the US Food and Drug Administration (FDA) for use on humans.

What Stones Should Not Be Together?

• All Sunstones should be kept away from stones that are associated with the planets Saturn and Venus.
• Quartz is incompatible with the following minerals: pearls, opal, and moonstone.
• Venusian and Mercury stones cannot be used with any gemstones associated with the planet Jupiter.

This means that even though the two can look the same, particularly their black variants when they are polished well enough, they are actually very different. The easiest way to differentiate between black onyx and black obsidian is by lifting them up since onyx is significantly denser and heavier than obsidian.

Apache Tear is really a sub-group or type of obsidian; essentially the same stone, both made of volcanic glass and black in color. However, Apache Tears are black obsidian that formed by being thrown up into the air giving them a much less glassy & more rough appearance.

The black obsidian stone is a potent cleanser of the psychic smog made within the aura, and is considered as a powerful psychic protection stone. This stone also has a powerful metaphysical properties, which may assist in shielding you against negativities. Its energies may stimulate the prophesy gift.

As a form of Obsidian, Apache Tears carry a very grounding vibration and are aligned to the Base or Root chakra. You can use it to connect with both your Earth Star chakra and with the Earth chakra at the center of the planet.