Mini Me Geology Blog » ask a geologist

Fire Rocks – Our new Ask-a-Geologist Question

tracyb — Fri, 22 Jan 2010 21:54:18 +0000

Question: Which rocks have the name that means fire?

Answer: The mineral name pyrite is derived from the Greek word for fire. It is believed that pyrite got its name because it will spark when it is struck against steel. Pyrite is a mineral that is most often known as “fool’s gold” due to its resemblance to the real thing.

Pyrite is silvery yellow in color and forms in cubes which have a shiny, metallic appearance. One of the best ways to tell pyrite from real gold is hardness. Gold is soft, while pyrite can not be scratched with a knife.

Visit us at www.MiniMeGeology.com for more great geology fun!

Metamorphic Q&A

tracyb — Mon, 21 Sep 2009 13:14:05 +0000

Question: What rocks are changed by high pressure and high temperature?

Answer: The change of a rock by high temperature and pressure is called metamorphism. This is the process by which metamorphic rocks are formed. Any rock can be changed by metamorphic processes.

Keep your questions coming. Submit them to us here and look for a reply from us here on our blog and on our website!

Today’s Ask-a-Geologist Question: Banded Textures

tracyb — Wed, 08 Jul 2009 15:17:10 +0000

Question: What term for metamorphic rock with banded texture?

Answer: You may be referring to “foliation” which is the layering within a metamorphic rock. Foliation occurs when there is a strong pressure applied to the rock in one direction, just like when you put your hands flat together and push. When this pressure is applied, certain minerals, like mica and chlorite, grow with their long direction perpendicular to the pressure. This make the rock appear with layering and/or banding.

New Ask-a-Geologist Question: Layered Rock

tracyb — Sat, 27 Jun 2009 13:41:10 +0000

Question: What is the term for the layering of sedimentary rock?

Answer: Often these rocks are called layered or banded rock. Sometimes people use the term “banded” when referring to layered rocks with distinct color or mineral changes. This photo of a banded sandstone shows the distinct layers or bands of the rock. In this case, the red color in some sandstone bands was caused by iron being deposited within the rock. The layers of a rock indicate a change in the composition of the material that makes up the rock such as the iron content or a change from mostly sand to mostly clay.

To see more unique rocks, visit www.MiniMeGeology.com.

Our Most Popular Ask-a-Geologist Question…..EVER!

tracyb — Mon, 22 Jun 2009 18:27:47 +0000

This has to be the most-asked question we receive here at Mini Me Geology. There must be a middle school or high school text book or worksheet out there that is used by many schools in the country. I think the question is worded a little funny, but here is the question and answer. For all of you teachers out there, take a look at this question….I think the weird wording is throwing the students off because I have been asked this question (worded exactly the same) dozens of times!

Question: What are the hollow ball-like objects, such as quartz, which are found in sedimentary rocks?

Answer: By “hollow ball-like objects” I believe you are thinking of geodes. Geodes are round in shape and hollow in the center. Geodes are usually filled with crystals such as quartz and amethyst. This photo shows several unopened geodes and some that have been cracked open with a rock hammer. The open geodes show the layers of quartz on the inside. Geodes form when an opening (hole) is present in a sedimentary or sometimes igneous rock. Silica-rich waters fill the opening and begin depositing agate and quartz crystals into the opening.

To purchase your own geodes, visit the Unique Rocks & Minerals section at www.MiniMeGeology.com. You will receive a set of 4 large (2″+) geodes that you can crack yourself. Full instructions for both cracking the geodes and doing it safely are provided.

Here are some of our latest “Ask-a-Geologist” questions & answers

tracyb — Wed, 16 Jul 2008 06:27:39 +0000

Q: What is in magma that makes up a rock?

A: Magma is the term used for liquid rock which forms deep below the Earth’s surface. Magma can be composed of many different things such as silicates, alkalis, iron and magnesium. The composition of the magma will determine the type of rocks which it will eventually form.

Q: What rocks are changed by high pressure and high temperature?

A: The change of a rock by high temperature and pressure is called metamorphism. This is the process by which metamorphic rocks are formed. Any rock can be changed by metamorphic processes.

Q: What term for metamorphic rock with banded texture?

A: You may be referring to “foliation” which is the layering within a metamorphic rock. Foliation occurs when there is a strong pressure applied to the rock in one direction, just like when you put your hands flat together and push. When this pressure is applied, certain minerals, like mica and chlorite, grow with their long direction perpendicular to the pressure. This make the rock appear with layering and/or banding.