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Obsidian, igneous rock occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes. Obsidian is extremely rich in silica (about 65 to 80 percent), is low in water, and has a chemical composition similar to rhyolite. Obsidian has a glassy lustre and is slightly harder than window glass.
Why is obsidian glassy?
Obsidian is a glassy igneous rock that usually forms as an extrusive, fast-flowing lava. When the lava cools so rapidly that atoms can’t form into a crystalline structure, this glassy rock is the result. This means that the different mineral atoms begin to react with each other and form crystals.
What does glassy mean in rocks?
If a rock looks like a block of (colored) glass, with no visible mineral crystals, it has a glassy texture. Superficially, a glassy texture suggests cooling that was so extremely fast that no crystals could form.
How do you describe the texture of a rock?
The texture of a rock is the size, shape, and arrangement of the grains (for sedimentary rocks) or crystals (for igneous and metamorphic rocks). Also of importance are the rock’s extent of homogeneity (i.e., uniformity of composition throughout) and the degree of isotropy.
What are three types of igneous bodies?
When molten rock, or melted rock, solidifies, igneous rocks are formed. There are two types of igneous rocks: intrusive and extrusive.Extrusive Igneous Rocks
- andesite.
- basalt.
- dacite.
- obsidian.
- pumice.
What does porphyritic texture mean?
A porphyritic texture displays minerals in two distinct size populations: one or more minerals are consistently larger than the rest of the minerals in a rock. The extra large mineral grains are called phenocrysts. Porphyritic textures are found in rocks with both coarse- and fine-grained groundmasses.
What is the most common type of extrusive rock?
The most common extrusive igneous rock is basalt, a rock that is especially common below the oceans (Figure 4.6). Figure 4.5: Extrusive or volcanic igneous rocks form after lava cools above the surface.
What does Obsidian feel like?
What does Obsidian feel like? Obsidian has a strong conchoidal fracture and luster. It means that the top of the fracture is curving smoothly (like a seashell).
Is Obsidian really strong in real life?
Unlike in Minecraft, real life obsidian is only mildly hard (pickaxe) (five on the Mohs scale), and very brittle (tnt). That’s because obsidian is glass, and rather than being super tough, it’s brittle, shattering easily.
Is Obsidian valuable?
There is no set value or market for obsidian, unlike silver and gold, where there are world markets and indices. Obsidian is not an expensive stone. This being the case, a piece of obsidian can cost $2 or $100 depending on the quality and processing it has undergone, you can shop at Amazon.
Is Obsidian rare?
Obsidian is found in many locations worldwide. It is confined to areas of geologically recent volcanic activity. Obsidian older than a few million years is rare because the glassy rock is rapidly destroyed or altered by weathering, heat, or other processes.
What crystals should not be together?
Conflicting Crystals: Which Crystals to Avoid Using Together
- Clear Quartz and The Wrong Crystal.
- Tiger’s Eye and Smoky Quartz.
- Orange Calcite and Blue Lace Agate.
Where should I put black obsidian in my house?
Put one anywhere near the front door of your house – many people’ll pop one in a pot plant, or above the door frame. Obsidian and hematite are also used in this way, as they’re also known for their protective qualities.
What do intrusive igneous rocks look like?
Intrusive igneous rocks crystallize below Earth’s surface, and the slow cooling that occurs there allows large crystals to form. Examples of intrusive igneous rocks are: diabase, diorite, gabbro, granite, pegmatite, and peridotite. Dacite is a fine-grained, extrusive igneous rock that is usually light in color.
What’s the texture of obsidian?
Obsidian is an extreme variety of igneous rock with a glassy texture. Most popular accounts say that obsidian forms when lava cools very quickly, but that is not quite accurate. Obsidian starts with lava very high in silica (more than about 70 percent), such as rhyolite.
Are glassy rocks intrusive or extrusive?
Igneous rocks may be simply classified according to their chemical/mineral composition as felsic, intermediate, mafic, and ultramafic, and by texture or grain size: intrusive rocks are course grained (all crystals are visible to the naked eye) while extrusive rocks may be fine-grained (microscopic crystals) or glass (
What is one way a glassy texture forms?
What is one way a glassy texture forms? Lava cools slowly.
What crystals should not be in your bedroom?
CRYSTALS TO AVOID NEAR THE BED:
- • Don’t store your crystals under your bed.
- • Avoid very large crystals near the head of the bed.
- • Spiritual or ‘high vibration’ crystals can be over stimulating.
- • Never place Crystal Points, pointing directly at your head.
- • Fire element crystals can be over energising.
What does a rock’s texture reveal about its history?
Chapter 10
| Question | Answer |
|---|---|
| What does a rock’s texture reveal about its history? | Tiny sand-like grains or larger particles of broken rock indicates that the rock formed from sediments. long thin grains could be the result of heat or pressure squishing or stretching the rock. |
Is Obsidian dangerous?
In George R.R. Martin’s books, as well as in real life, obsidian can be extremely dangerous. This means the obsidian breaks into pieces with curved surfaces that are razor thin and extremely sharp. Over time, ancient peoples learned to break obsidian into tools of various shapes.
What is the texture of metamorphic rocks?
TEXTURES Textures of metamorphic rocks fall into two broad groups, FOLIATED and NON-FOLIATED. Foliation is produced in a rock by the parallel alignment of platy minerals (e.g., muscovite, biotite, chlorite), needle-like minerals (e.g., hornblende), or tabular minerals (e.g., feldspars).
What rocks has a glassy texture?
Obsidian is the common rock that has a glassy texture, and is essentially volcanic glass. Obsidian is usually black. Now let us briefly consider textures of tephra or pyroclastic rocks. Like lava flow rocks, these are also extrusive igneous rocks.
What does obsidian look like in real life?
Obsidian has a glassy lustre and is slightly harder than window glass. Though obsidian is typically jet-black in colour, the presence of hematite (iron oxide) produces red and brown varieties, and the inclusion of tiny gas bubbles may create a golden sheen.
What is Obsidian good for?
Healing Properties A strongly protective stone, it forms a shield against negativity. It blocks psychic attack and absorbs negative energies from the environment. Obsidian draws out mental stress and tension. It stimulates growth on all levels, urging exploration of the unknown and opening new horizons.
