How to identify raw jade in a rock

You cannot identify raw jade in a rock by looks. Jade in the rough is a dense, very tough, fine-grained rock, usually hidden under a dull weathered surface, and several common rocks look the same. What you can do at home is narrow it down in three steps: weigh the stone in water, try a knife point on an inconspicuous spot, and study a wet or freshly exposed surface. A specific gravity well below 2.9, or a knife that cuts in easily, rules a rock out. A rock that passes all three is a candidate, and a laboratory makes the identification.

This page is about recognizing rough and avoiding the scams around it. What rough jade is and how it is traded is covered in raw jade.

What raw jade looks like

Raw jade is a rock, not a crystal. Both jadeite and nephrite are metamorphic rocks made of tiny interlocking mineral grains, which is why they are so tough and why you will never see crystal faces. Loose pieces are usually stream-worn pebbles to boulders, and Geology.com’s gemologist author notes that such boulders typically carry a brown weathering rind that hides the interior.

Nephrite is the jade of North America. The Wyoming State Geological Survey describes it as an extremely dense, compact mass of felted, fibrous amphibole. Color runs from white to black, most of it shades of green (apple, emerald, leaf, olive), and it is translucent to opaque. Where it is broken, the fracture is irregular and splintery with a dull surface. On a clean or wet surface the luster is vitreous to greasy, silky or waxy. More on the stone itself is in nephrite jade.

Jadeite is granular, not fibrous, with a vitreous to sugary luster. Rough from Myanmar comes as boulders with a skin that can be white, yellow, light to dark brown or black, tough enough that it usually has to be ground off. It is not something a North American rockhound normally finds: the Wyoming survey notes that jadeite has been reported in the state but never verified. The two are compared in jadeite versus nephrite.

Three home checks, with numbers

1. Weigh it in water

Specific gravity is the most useful home test for rough, because jade is denser than most lookalikes. Weigh the stone dry, weigh it again hanging fully submerged in water from a thread, and divide the dry weight by the difference.

Result	Consistent with
About 2.9 to 3.02	Nephrite
About 3.34	Jadeite
2.65	Quartz and quartzite
About 2.5 to 2.8	The common jade-like serpentines

A small piece needs a scale that reads to 0.01 g, and bubbles clinging to a rough surface will throw the result off.

2. Try a knife on a hidden spot

A knife blade is about 5.5 on the Mohs scale. It should not cut into jadeite (6.5 to 7) and normally not into nephrite (6 to 6.5, though the Wyoming survey gives 5.5 to 6.5 for rough). Serpentinite, the most common green lookalike, is soft and scratches easily.

Steel can leave a gray metal streak on a hard stone. Wipe it: a streak comes off, a real scratch stays. And a stone that resists the knife is not thereby jade, since quartz, at 7, resists it too. Jade’s defining property is toughness, which is a different thing from scratch hardness and is explained in jade hardness.

3. Read a wet or fresh surface

Wet the stone and look at the luster under a good light. Nephrite looks oily and soft, which is how Chinese nephrite dealers put it too, while quartzite looks glassy. Freshly broken quartzite sparkles and shows curved, shell-like (conchoidal) fracture. Aventurine quartz sparkles from mica flakes.

A magnet adds one more clue: the Wyoming survey lists serpentinite as weakly to moderately magnetic.

Rocks mistaken for jade

Rock	How it differs from jade
Serpentine and serpentinite	Soft enough for a knife to scratch, specific gravity about 2.5 to 2.8, weakly to moderately magnetic
Quartzite, including green fuchsite-bearing quartzite	Specific gravity 2.65. Fresh breaks sparkle and show conchoidal fracture
Aventurine quartz	Sparkles from mica flakes
Chalcedony and chrysoprase	Lower specific gravity than jade
Epidote	Perfect cleavage and a pistachio-green color
Californite (vesuvianite), sold as “California jade”	Specific gravity 3.32 to 3.47 and hardness 6.5, so it passes both tests. It is less tough and breaks more easily
Hydrogrossular garnet (“Transvaal jade”), green jasper (“Oregon jade”)	Jade in name only

The Wyoming survey also lists amphibolite, metadiabase and pale granite among the rocks mistaken for nephrite. Serpentinite deserves particular suspicion because it keeps company with nephrite: the two are found together in British Columbia and on the California coast.

How to identify California jade

The name is the problem. “California jade” is a trade name for californite, a green massive vesuvianite from Siskiyou County, near Happy Camp. It is neither jadeite nor nephrite, and according to Gemdat its density and hardness overlap jadeite’s, so the water and knife checks will not catch it. That takes a laboratory.

California does have both true jades. At Jade Cove on the Big Sur coast, nephrite sits in pods and nodules within serpentine bedrock and erodes out as pebbles and larger stones on the shore and seabed. Jadeite deposits in the Clear Creek area of San Benito County were described in the scientific literature in 1961.

Where else raw jade turns up, and the rules on collecting it

• Wyoming. Most high-quality nephrite has come from alluvial deposits in and around the Granite Mountains in the center of the state, as stream-rounded pebbles and boulders.
• British Columbia. According to the British Columbia Geological Survey, nephrite forms lenses at or near the contacts between serpentinite and other rocks, and loose blocks in boulder fields and talus are worked as well.

Collecting rules depend on who owns or manages the land, and they change. Jade Cove shows how specific they get. A 1998 federal rule for the Monterey Bay National Marine Sanctuary allows collecting only loose pieces, between the mean high tide line and a depth of 27 m (90 ft), in a defined stretch between Sand Dollar Beach and Cape San Martin. You may take only what one person can carry and use only a hand tool no longer than 91 cm (36 in), which may scratch a stone to test it but not break or chip it. The rule itself notes that a California state permit is needed on state submerged lands and that collecting on the adjoining national forest land is restricted. Check the current rules for any site before you collect.

If someone is offering you rough

Jadeite boulders are sold on the evidence of their skin and of small polished windows, and buying one is a gamble even for professionals; the raw jade page explains how that market works. Fraud is a separate risk. The Gems & Gemology study of the Burmese jade trade documents these tricks on boulders:

• a window stained green on the surface
• a chip broken off, dyed green and glued back, so that a window cut there shows color
• a boulder drilled almost through, filled with green glue and plugged with epoxy mixed with ground skin
• a core sawn out and replaced with green material and a reflector
• a wholly artificial skin over a ground-down, stained surface

A fake skin betrays itself by being soft. Genuine skin is part of the stone and as hard as the jade beneath it, while an artificial one comes off easily. A Chinese rough dealer shows this on a boulder that had been knocked about: wherever it was hit, the coating had chipped away to bare white stone, which a real weathered skin does not do. The stone under that fake skin was real jadeite, of poor quality.

Nephrite has its own version. River pebbles, called ziliao (籽料), carry a premium in the Chinese market, so dealers describe quarried nephrite being tumbled into pebble shapes and dyed or baked to give it a red-brown skin, and genuine pebbles being given a more desirable skin by sandblasting, acid etching and dye. The fine surface pitting that buyers are told to look for is now imitated well enough that an experienced dealer says she cannot always tell real from fake.

A laboratory report does not solve this. It normally confirms that the stone is nephrite, which the imitation also is, without confirming that the pebble form or the skin is natural.

What a laboratory does, and whether it is worth it

Positive identification of rough needs a laboratory. The Wyoming survey says that telling the jades apart, and telling them from lookalikes, often requires petrographic, specific gravity, geochemical or X-ray diffraction analysis.

Before paying for that, remember that being jade does not make a rock valuable. The Wyoming survey states that only about 10 percent of most nephrite deposits is gem quality. Quality depends on uniform texture, absence of inclusions, color intensity and translucency, and schistosity or fine fractures reduce it drastically. For finished pieces, the home tests and their limits are set out in how to tell if jade is real.