To know how best to cut petrified wood, you’ll have to learn some plant anatomy, and to describe and label petrified wood, you’ll need to learn more plant anatomy and buy a 20X lens: your old 10X loop isn’t powerful enough. One attraction of petrified wood, seldom taken advantage of by lapidaries, is telling its story: petrified wood was once alive, and most people are interested in fossils. This can vary from describing woody features to telling how long ago the tree was alive to identifying what kind of tree it was.
CUTTING, GRINDING AND GLUING
When cutting petrified wood, take a hint from how sawmills cut logs and vary the angle of cut to fit the variety of tree being cut. Most logs are “board-cut,” a cut made parallel to the length of a log that doesn’t go through the pith in the center (a/k/a “tangential cut,” per wood scientists). Board-cuts show annual growth rings as repetitive, wavy, oval or “V” or “U” shaped patterns, as can be seen on plywood and dimensional lumber. These patterns will differ, of course, based on whether the board cut is made closer to the outside of a log or closer to its center. Board cuts, however, will create such patterns only if you’re cutting trees that grew in a temperate climate, which have growth rings marking the seasonality of wood growth from spring to the annual dormant winter season.
Tropical trees, in contrast, grow year around and so lack annual growth rings; when board-cut, they won’t show such attractive patterns. In the western U. S., most petrified wood older than the mid-Eocene (about 48 million years ago) grew in the tropics and lacks growth rings. If you collect petrified wood specimens in the field, you can easily learn how long ago those trees were alive by contacting the federal or state land management agency closest to your collecting area, or you can check geologic maps. The very old petrified trees from Arizona and Utah, dating to the Jurassic and late Triassic, lack annual growth rings because they grew in the tropics; they may, though, have a few sporadic rings marking droughts. Much such petrified wood is so colorful it’s called “rainbow wood” and will show bright, attractive colors however it is cut. Other highly colorful varieties of petrified wood, like “Roxy Ann wood” from southwest Oregon, can also make attractive cabs regardless of the angle cut, as shown in the nearby photo.
TEMPERATE CLIMATE TREE PATTERNS
Temperate climate trees can also reveal attractive patterns if “cross-cut,” a cut made perpendicular to the length of the log. This is the cut timber fallers make at the base of a tree trunk to drop the tree (a/k/a “transverse cut”). When a tree with growth rings is cross-cut, its rings show as concentric circles, like a bull’s eye target, and its rays – which carry nutrients from a tree’s outer, living sapwood to its center – show as narrow lines going across, and at right angles to, these rings. In round limbs, rays look like the spokes of a wheel as shown in the nearby drawing but appear to be nearly parallel lines in chunks of petrified wood from big limbs or logs.
While board-cut, temperate climate trees sometimes show growth rings as wide, wavy patterns too large to capture in a small cab. Cross-cuts of such trees will usually capture smaller patterns that both fit within a cab and are often appealing to the naked eye. Before making my first cab, I’d spent 10 years cutting petrified wood specimens, and every one of those cuts was a cross-cut because I was obsessed with identifying wood varieties. To identify wood with a 20X lens, you must study the cross-sectional face of a limb’s vascular system (“plumbing system”), which moves water up from roots to leaves.
Trees with bold growth rings can be showy both when cross-cut and when board-cut. Wood anatomists call these trees “ring porous” because they develop large pores in the spring to carry water from roots to growing leaves, but only small pores in the summer; this contrast prominently marks annual growth rings. Ring porous trees include oak, locusts, ash, sassafras, and elm. In contrast, “diffuse porous” hardwoods – like willow, poplar, cherry, and maple - lack bold growth rings because there is no noticeable difference in pore size throughout the year.
Conifers, which evolved earlier with a less efficient plumbing system, move water from roots to needles through a mass of tiny, straw-like structures called “tracheids.” When viewed with a 20X lens in cross-section, masses of tracheids look like a close-up view through a window screen, and even a sudden change in tracheid size from larger in spring to smaller in summer may not be eye-catching when seen with the naked eye.
Continue reading your story on the app
Continue reading your story in the magazine
Easy Pickins' at Australia's Agate Creek
As a member of a few Australian Facebook fossicking (rockhounding) groups, I had been seeing photos of an amazing variety of cut and polished agates posted by people who had found them at Agate Creek.
Elizabethan Gems; Literal and Literary
MINERALS TO BEWARE OF Myrickite
Some venomous snakes and stinging wasps and bees advertise their dangerous nature with bold red, yellow, and orange colors that seem to say, “Stay away!”
Hell's Canyon Petrified Wood
WHAT TO CUT
Benitoite’s Uncommon Partner
Nafplio Archeological Museum
Bronze Age Jewelry Rival Contemporary Designs
A Different Decoration From the Back
Volcanoes Continue to Capture Headlines
EARTH SCIENCE IN THE NEWS
SMITHSON, SMITHSONITE, AND THE SMITHSONIAN
“PETOSKEY STONE” Michigan's State Stone
Apple Won't Let Fortnite Back Until Case Ends
Tim Sweeney, CEO of Fortnite maker Epic Games Inc., said Wednesday it’s been told by Apple that the game will be “blacklisted from the Apple ecosystem” until the companies’ legal case is resolved and all appeals are exhausted, which could take as long as five years.
CALIFORNIA 1ST TO SET QUOTA LIMITS FOR RETAILERS LIKE AMAZON
California became the first state to bar megaretailers from firing warehouse workers for missing quotas that interfere with bathroom and rest breaks under a new law signed by Gov. Gavin Newsom that grew from Amazon’s drive to speed goods to consumers more quickly.
FACEBOOK OVERSIGHT BOARD REVIEWING ‘XCHECK' SYSTEM FOR VIPS
Facebook’s semi-independent oversight board says it will review the company’s “XCheck,” or cross check, system following an investigation by The Wall Street Journal into the use of this internal system that has exempted high-profile users from some or all of its rules.
CHINA'S ANT GROUP TO SHARE CREDIT DATA WITH CENTRAL BANK
China’s central bank will soon have access to the private credit information of hundreds of millions of users of Ant Group’s online credit service, in a move signaling more regulatory oversight of the financial technology sector.
NETFLIX BUYS WONKA AUTHOR DAHL'S CATALOG
Netflix has acquired the works of Roald Dahl, the late British author of celebrated children’s books such as “Charlie and the Chocolate Factory.”
APPLE, GOOGLE RAISE NEW CONCERNS BY YANKING RUSSIAN APP
Big Tech companies that operate around the globe have long promised to obey local laws and to protect civil rights while doing business.
CHINA SETS UP PLATFORM TO POLICE GAMING FIRM VIOLATIONS
Chinese regulators have set up a platform that allows the public to report on gaming companies they believe are violating restrictions on online game times for children.
ONE TO CHARGE THEM ALL: EU DEMANDS SINGLE PLUG FOR PHONES
The European Union unveiled plans Thursday to require smartphone makers to adopt a single charging method for mobile devices.
DON'T LET SOCIAL SECURITY STEER YOU WRONG
Few retirement decisions are as critical, or as easy to get wrong, as when and how to take your Social Security benefits.
AT LONG LAST, BALLMER, CLIPPERS BREAK GROUND ON NEW HOME
The design meetings have been going on for years.