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Hobart M. King

Dr. Hobart King

Hobart M. King, Ph.D., is the publisher of He is a geologist with over 40 years of experience and is a GIA graduate gemologist. Much of his work has focused on coal geology, industrial minerals, gemology, geologic hazards, and geoscience education.

He has authored many of the internet’s most popular articles about rocks, minerals and gems. He writes most of the content published on and compiles its daily news. His writing is read by over a million people each month, making him one of the world’s most widely read geologists.

Dr. King earned a Ph.D. and an M.S. in geology from West Virginia University; a B.S. in geology from California University of Pennsylvania; and, a Graduate Gemologist Diploma from the Gemological Institute of America. He is a Registered Professional Geologist in the Commonwealth of Pennsylvania.

Prior to he worked on research projects related to the geochemistry and mineralogy of coal and shale at West Virginia University between 1975 and 1982; worked at the West Virginia Geological and Economic Survey as a coal geologist, economic geologist and Head of the Economic Minerals and Geologic Hazards Section between 1980 and 1994; taught as an adjunct professor of geology at two Pennsylvania State University campuses between 1988 and 1994; and was a geology professor at Mansfield University of Pennsylvania between 1994 and 2008. He has been owner and publisher of since 2005.

Articles written by Hobart King appear below and in his Google Scholar profile.

Shale The rock that is quickly transforming the energy industry.
Corundum is the third-hardest mineral. It is also the mineral of ruby and sapphire.
Homeowners Insurance
Homeowners Insurance
Homeowners Insurance usually does not cover the most common geologic hazards.
Diamonds from Coal?
Diamonds from Coal
Biggest Misconception Lots of people think that diamonds form from coal. Not True!
Mineral Hardness
Mohs Hardness Test
Mohs Hardness Scale is a set of reference minerals used for classroom hardness testing.
Utica Shale
Utica Shale
Utica Shale A giant reservoir of natural gas, oil, and natural gas liquids below the Marcellus.
Salt Domes
Salt Domes
Salt Domes - Salt structures that are often associated with oil and natural gas.
Tanzanite was unknown until a few decades ago but it has erupted into wide popularity.
Ruby and Sapphire
Ruby and Sapphire
Ruby and Sapphire are the 2nd and 3rd most popular colored stones in the United States.
Fluorescent Minerals
Fluorescent Minerals
Fluorescent Minerals and rocks glow with spectacular colors under ultraviolet light.
Ethiopian Opal
Ethiopian Opal
Ethiopian Opal - The new opal heavyweight that might give Australia a run.
Topaz is a popular birthstone and the #8 mineral in the Mohs Hardness Scale.
Rare Earth Elements
Rare Earth Elements
Rare Earth Elements are used in cell phones, DVDs, batteries, magnets & many other products.
Soapstone is a metamorphic rock with properties that make it suitable for a variety of projects.
Quartzite a nonfoliated metamorphic rock composed almost entirely of quartz.
The Brewery Rock ?
Making Beer With Rocks - Do you know which fossiliferous rock is used to make beer?
Garnet is best known as a red gemstone. It occurs in any color and has many industrial uses.
Moldavite is a gem material born about 15 million years ago when a pair of asteroids struck Europe.
Wrong Volcano! The most powerful eruption of the 20th century was misidentified?
Geodes look like ordinary rocks on the outside but can be spectacular inside!
The Acid Test
The Acid Test
The Acid Test Geologists use dilute hydrochloric acid to identify carbonate minerals.
Coal Close Up
Coal Through a Microscope Coal is more than a black rock. It's THE most interesting rock.
Frac Sand
Frac Sand
Frac Sand The amount of frac sand produced in the USA is up by over 300% since 2009.
Lapis Lazuli
Lapis Lazuli
Lapis Lazuli - a metamorphic rock and the most popular blue opaque gemstone in history.
Olivine is a rock-forming mineral found in the crust, the mantle, and in some meteorites.
Emerald is the most popular green gemstone in the United States and most of the world.
Uses of Gold
Uses of Gold
The Many Uses of Gold Unique properties make gold one of the most useful metals.
Petrified Wood
Petrified Wood
Petrified Wood is a fossil that forms when dissolved material precipitates and replaces wood.

Articles About Rocks

Amphibolite Marble
Andesite Novaculite
Basalt Obsidian
Breccia Pegmatite
Caliche Peridotite
Chert Pumice
Coal Quartzite
Conglomerate Rhyolite
Diatomite Sandstone
Diorite Schist
Dolomite Scoria
Flint Shale
Gabbro Siltstone
Gneiss Slate
Granite Soapstone
Iron Ore Tuff

Articles About Minerals

Andalusite Ilmenite
Anhydrite Jadeite
Apatite Kyanite
Arsenopyrite Limonite
Augite Magnesite
Azurite Magnetite
Barite Malachite
Bauxite Monazite
Beryl Muscovite
Biotite Nephrite
Bornite Olivine
Calcite Orthoclase
Cassiterite Plagioclase
Chalcopyrite Pyrite
Chlorite Quartz
Chromite Realgar and Orpiment
Chrysoberyl Rhodochrosite
Cinnabar Rhodonite
Copper Scapolite
Cordierite Serpentine
Corundum Silver
Diamond Sodalite
Diopside Sphalerite
Dolomite Spinel
Epidote Spodumene
Feldspar Staurolite
Fluorite Sulfur
Fuchsite Talc
Galena Titanite
Garnet Topaz
Gold Tourmaline
Graphite Turquoise
Gypsum Variscite
Halite Zircon
Hematite Zoisite

Articles About Gemstones

Amethyst Labradorite
Ametrine Lapis Lazuli
Ammolite Maw Sit Sit
Ant Hill Garnet Moldavite
Aventurine Opal
Azurmalachite Peanut Wood
Bloodstone Polka Dot Agate
Brown Diamonds Prasiolite
Chrysoprase Red Beryl
Emerald Rose Quartz
Fancy Sapphire Ruby and Sapphire
Gem Silica Smoky Quartz
Goldstone Strontium Titanate
Helenite Sunstone
Heliodor Tanzanite
Iris Agate Tiffany Stone
Jade Turritella
Jet Unakite
General Geology

Articles About General Geology

Blood Diamonds Hydraulic Fracturing
What is a Caldera? World Lightning Map
Canadian Diamond Mines Liquefied Natural Gas
Crater of Diamonds Marcellus Shale
Crushed Stone Methane Hydrates
Difficult Rocks Mineral Rights
Eagle Ford Shale Mohorovicic Discontinuity
Expansive Soil Oil Sands
Gem Diamond Map Ticks and Lyme Disease
Geysers Titanium
Green River Fossils Trap Rock
Helium Volcanic Ash
Herkimer Diamonds Water Dowsing
Horizontal Drilling  
More General Geology
  Land Below Sea Level
  What Does a Geologist Do?
  Waterproof Paper
  Divisions of Geologic Time
  Plate Tectonics
  What Is Earth Science?

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Ruby and Sapphire are the 2nd and 3rd most popular colored stones in the United States.