Fly Ranch Geyser, Gerlach, Nevada
Theodore Clutter
Minnetonka Cave #1
William H. Mullins
Minnetonka Cave
William H. Mullins
Mammoth Cave
John W. Bova
Chrysocolla Deposit
Charlie Ott
Volcanic Deposits In Stream, Ecuador
William H. Mullins
Stalactite #1
Ted Kinsman
Fly Ranch Geyser
Theodore Clutter
Fly Ranch Geyser #1
Theodore Clutter
Malachite
Hermann Eisenbeiss
Castle Geyser, Yellowstone
David Hosking
Beauty Pool, Yellowstone
David Hosking
Lake Magadi, Kenya
Gregory G. Dimijian, M.D.
Ammonite Chambers
Martin Shields
Painted Cliffs, Maria Island, Tasmania
David Hosking
Death Valley, Ca #7
Richard and Ellen Thane
Death Valley, Ca #10
Richard and Ellen Thane
Twin Domes, Carlsbad Caverns
Tracy Knauer
Icelandic Hot Springs
Greg Dimijian
Longfellows Lake, Carlsbad Caverns
Bruce Roberts
Linville Caverns #1
Millard H. Sharp
Hibernating Bat, Linville Caverns
Millard H. Sharp
Lehman Caves
Richard W Brooks
Lehman Caves #1
Richard W Brooks
Linville Caverns
Millard H. Sharp
Cenote Of Dzitnup
J. Gerard Sidaner
Seven Star Cave, China
George Holton
Florida Caverns State Park #10
Millard H. Sharp
Linville Caverns #2
Millard H. Sharp
Linville Caverns #4
Millard H. Sharp
Linville Caverns #5
Millard H. Sharp
Linville Caverns #6
Millard H. Sharp
Linville Caverns #7
Millard H. Sharp
Mitchell Caverns
Richard W Brooks
Reed Flute Cave, China
George Holton
Seven Star Cave, China #1
George Holton
Linville Caverns #3
Millard H. Sharp
Milky Quartz Boulders
Kenneth Murray
Coal Surface Mine
Inga Spence
Sulfur Deposits
Stephen & Donna O'Meara
Azurite And Malachite
Gerard Lacz
Pyromorphite From Bad Ems, Germany
Joel E. Arem
Salton Sea Salt
Ted Kinsman
Salton Sea Salt #1
Ted Kinsman
Wulfenite From Theba, Arizona
Joel E. Arem
Salt Pan In Death Valley
George Ranalli
Devils Golf Course
George Ranalli
Tiny Fumaroles
Gregory G. Dimijian, M.D.
Bonneville Salt Flats, Utah
William Belknap
Salt Pan In Death Valley #1
George Ranalli
Fumaroles In Yellowstone
Gregory G. Dimijian, M.D.
Salt Ponds In California #1
Richard Hansen
Salt Flats In Death Valley
Dennis Flaherty
Salt Encrusted Basin
Inga Spence
Salt Encrusted Basin #2
Inga Spence
Salt Ponds In California
Richard Hansen
Vanadinite From Mibladen Morocco
Joel Arem
Limestone Pit
Inga Spence
Pamukkale, Turkey
Alison Wright
Vanadinite From Mibladen, Morocco
Joel E. Arem
Silver From Germany
Joel E. Arem
Gypsum From Cherokee Flats, Oklahoma #1
Joel E. Arem
Pamukkale, Turkey
Kenneth Murray
Fluorite From Weardale, England
Joel E. Arem
Diamond, Crystal In Matrix
Joel E. Arem
Open Pit Mines, Southern Arizona
NASA/Science Source
Travertine Falls, Grand Canyon, Az #1
William H. Mullins
Travertine Falls, Grand Canyon, Az #2
William H. Mullins
Stalactites & Stalagmites #1
Spencer Sutton
Surface Coal Mine #1
Inga Spence