Have you ever read a rockhounding guide and come across a sentence like this - "The material is often found as float along the creek bed" - and wondered just what it meant?

Rest assured, it doesn't mean that the rocks can float!

Float is a term use to describe loose chunks of rocks that have broken free of the rock formation they originally formed in, and often have travelled some distance, either carried by a stream, or by rolling downhill.

Float is often very useful for finding interesting rock formations - look for the pieces, and then follow the trail of rocks as best as you can until you find where they originally came from.

Unfortunately, it's often hard to know just how far a piece of float may have travelled before you found it. Did it break off the cliff five yards upstream and get carried down last winter? Or was it carried three hundred miles by a glacier that melted away thousands of years ago?

How can you tell?

The first thing to look for is how well-rounded the piece is. If it's very smooth, it has likely travelled a long way in water, polished by other rocks and debris as it went along. If it has sharp, jagged edges, it's more likely to have come from someplace nearby.

If there are many other rocks around that look similar, then you are probably very close to the source. Look up - uphill, upstream, upriver - and if you find it, give yourself a big pat on the back. Well done!

As a beginning rockhound, you might have wondered what tools and equipment you will need to start out in this hobby.

Fortunately, the basic tools you'll need are not particularly expensive or complicated. Here's a list of a few to get you started!

• Rock Pick  - The rock pick is the most basic rockhounding tool. You'll want it for breaking open rocks to reveal their interiors, for removing specimens from stubborn chunks of matrix, and for digging or prying rocks from the ground.
• Safety Goggles  - If you're using the rock hammer, you need safety goggles as well. It's easy to cause chips to fly when you're working with rocks, and if you don't use appropriate eye protection, you risk serious eye damage. Wear your goggles!
• Rock Chisel  - Chisels can be used along with your hammer, to assist in removing specimens from the matrix stone, and to give you better precision and control than the hammer alone will provide.
• Magnifying Loupe  - This tool will allow you to take a close look at your rock, and see structures or features you might not be able to see with your bare eyes. Very handy for identifying your finds!
• Sturdy backpack  - You'll probably be hauling a lot of heavy objects around, so make sure your backpack is sturdy enough to contain them. I once had a pack rip right open on a field trip, and dump all my finds on the ground - it wasn't fun!
• Good shoes and appropriate clothing  These speak for themselves, but sometimes people forget. Shoes are particularly important, due to sharp rocks, snakes, thorns, and sundry other rockhounding hazards.
• Ear plugs - using chisels and rock hammers can become very noisy
• Hard Hat  - You only really need a hard hat if you're going to be collecting rocks near steep slopes, in a pit, or in a mine - basically, anywhere you could stand and bump your head, or where a dislodged object could fall upon you from above. Head injuries are not something you want to risk, however unlikely you think they may be. Be safe.

That should be enough to get you started in the hobby. If you think of something that should be on this list and isn't, leave me a comment below!

Happy hunting, and stay safe out there.

Geology can be spectacular.

​On a recent trip to Texas, I stopped by the Inner Space Cavern near Georgetown for a guided tour of the cave, and spent a few hours admiring all the limestone formations (and fossils!) 

The cavern is thought to be about 100 million years old, though the vast majority of that time has been spent sealed off from the world, deep underground. 

Between 45 and 20 million years ago, during the Ice Age, sinkholes opened up which provided an entrance to the outside world - evidenced by the remains of the unfortunate mammoths, saber-tooth cats, and peccary who fell in (presumably trying to drink from water-filled sinkholes) and were unable to escape. 

About 14,000 years ago all the natural entrances closed up again, and the cave was again lost to time -- until the 1960s, when a Texas Highway Department crew accidentally drilled through the ceiling and lost an expensive drill bit, promptly sending one of their men down to retrieve it. Thus the caves were discovered.

And here is the tale of the discovery, written by the second person to ever enter the caves, Texas Highway Dept geologist James Samson. I shall leave him to tell the story, since I cannot hope to match it!

Chatoyancy or chatoyance, also known as the "cat's eye effect", is a visual effect seen in certain minerals, such as Tiger's Eye. When polished, chatoyant stones exhibit a bright streak of light that seems to move as you turn it.

Chatoyancy appears in minerals that have a fibrous nature, or fibrous inclusions. When the fibers are all aligned in the same direction, they reflect a streak of light that runs perpendicular to the alignment of the fibers.

The cabochon form - a smooth, polished dome-shape - is used to display chatoyancy. Make sure the fibers are aligned parallel with the base of the stone, for the best effect.

Quartz frequently displays this effect, as does beryl,  tourmaline, moonstone, and scapolite. Rarely, nephrite jade shows chatoyancy, particularly the material from the Big Sur Coast. Although beautiful, chatoyant jade can prove somewhat fragile and difficult to work with.

Who doesn't like rock books?

I like to collect rocks, but I also collect books. At a certain point, I learned to combine the two hobbies handily, and began to collect books about rocks.

A well-stocked bookcase is a must for the serious rockhound. From general geology books to identification guides to location field guides, a good book collection will expand your understanding of where to find your favorite rocks, and why they're there.

Here's a selection of a few of my favorite books for rockhounds.

A Field Guide to Rocks and Minerals (Peterson Field Guides) 
A Field Guide to Rocks and Minerals is one of my favorite rock-related books, mostly because it includes tests you can perform to confirm the identity of your rock or mineral. It is arranged by mineral class, which can make it more difficult for the ameteur to find the mineral they are looking for, but it has a wealth of useful information - I consult mine regularly.

National Audubon Society Field Guide to North American Fossils
North American Fossils is a wonderful resource. Although it does not have everything [or it would probably be too heavy to carry on your collecting trips] it focuses on the most common fossils in North America. The photographs show what the fossil looks like "in the wild" rather than all cleaned up and polished, as some books do, making it much more useful for actual identification purposes.

Gem Trails of Northern California
This is an excellent collecting guide, with maps to many different sites, and detailed summaries of what you can expect to find there. I have a look at mine before every trip I go on, just to see if there's any interesting sites nearby I should visit while I'm in the area.

Penguin Dictionary of Geology (Penguin Reference Books)
Ever run into some obscure geology term, where you just couldn't figure out what the heck it meant? This is the book for you. It's packed full of geological definitions, and you'll never have to wonder about another one. Plus, you can impress all the folks at the rock club by using words like "endometamorphism" in casual conversation.

Roadside Geology of Northern and Central California
This book is not aimed at collecting, but if you have an interest in geology, you'll love it. You'll learn about the geologic features you might drive past every day, and how they formed. The downside? You'll have to remember to pay attention to where the road is, and not stare off at the road cuts too much while you're driving.
Then again, you're a rockhound. You were already looking at the road cuts.