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How does a Star Ruby get its star?

Who made up the names for rocks and minerals?  Are they famous for anything else?

What minerals make granite?

Hi guys,
Good questions.  
The Star Ruby gets its star from many, many very tiny, very thin minerals called "rutile" that are inside the ruby.  They are called "inclusions" and that means that the ruby is not pure.  Rutile is a titanium mineral that can form into clusters that look like hair.  When they are super small and inside a ruby, they will bend light in such a way that it makes a six pointed star.  But, the ruby has to be cut into a specific shape called a "cabochon" (it looks like a little, round pillow) and only sunlight, or very strong artificial light, will bring out the star.  Still, they are rare since the rutile must be positioned just right, and the stone must be cut just right, and the light must be just right to see the star.  Artificial star rubies show very bright stars all the time, and that's how you know they are not real.  Incidentally, when a gem exhibits a star-like feature we call it "asterism".

Rocks and minerals were, and are, named by anyone.  From the ancient Romans who named volcanic rocks, "igneous", literally it means "fire", to modern day people.  Most of the common names for rocks and minerals were given in the past, and I am afraid that we really don't know who named most of them.  So they really aren't famous.  At least outside the realm of Geology.  Nowadays it requires painstaking analysis of a mineral's chemical, crystallographic, and physical properties to be sure that it is different from all other minerals, IN THE WORLD.  Then your new mineral name is submitted to the Commission on New Minerals and Mineral Names of the International Mineralogical Association.  Then they determine if it should be called a new mineral.  There are about 4,000 minerals that are named, but about 35,000 to 40,000 get turned down every year!

Granite is made up of three minerals, "quartz", "mica", and "feldspar".  Of course, since this is geology it isn't that simple.  There are variations, and there are percentages, and there are arguments.  But, generally, those three minerals are what makes a rock a granite.  

Quartz is the second most abundant mineral in the world and is made of the elements, silicon and oxygen.  All the sand you see when you go to the beach is quartz.  Mostly anyway.  Think of all the sand on all the beaches in the world and you get the idea.  

Mica is a mineral that's made of lots of different elements.  Iron and Sodium, Calcium and Barium, Aluminum and Magnesium, and more.  A large part is silica and oxygen, like quartz, but there is so many more elements that it is NOTHING like quartz.  One of the things about it is that it splits into sheets so thin that you can see through them.  In the old days people used it for glass in windows and furnaces.  They used to call it "isinglass".

Feldspar is the most abundant mineral in the world. At least 60% of the Earth's crust is made up of feldspars.  Like quartz, it is basically silica and oxygen, and like mica it has a LOT of other elements in it.  Those different elements make a completely different mineral.  I looks different and acts different.  It's used in things like paint, plastics, rubber, and glass making.

Hope this helps.


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C. Robert Reszka, Jr.


I can answer any general geology question (rocks, minerals, stratigraphy, geomorphology etc.). My expertise is in the geology of the Michigan Basin, PreCambrian, Paleozoic and Recent. I can answer questions concerning mining and petroleum exploration and production and the laws concerning those activities. I can also answer questions concerning stratigraphy of the Michigan Basin. I will also answer questions about mineral and rock collecting in the Basin. I won`t be able to answer many specific questions on hydrology, geophysics or geochemistry. I may be able to answer very general questions in those venues.


I have been working for the State of Michigan for 36 years as a Geologist and a Resource Analyst. I have experience with Subsurface Geology and Petroleum Geology, mining in Michigan, and Sand Dune Mining and Protection issues.

Michigan Basin Geological Society

Decade of North American Geology.
Bedrock Geology of Michigan

BS Wayne State University

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