Black Beads Compared: Onyx, Obsidian, Tourmaline, Hematite and Lava

Black onyx, obsidian, black tourmaline, hematite and lava all give you a black bead, but they are 5 very different materials, and you can tell them apart in your hand. Onyx is an evenly colored, glossy chalcedony from the quartz family; obsidian is volcanic glass with a bright, glassy shine; black tourmaline is a crystal with fine lengthwise lines and a slightly uneven luster; hematite is a metallic gunmetal iron oxide that feels surprisingly heavy; and lava is light, porous basalt with a matte, pitted surface. Below is a side by side comparison, a section on each stone, and a checklist for telling them apart.

All 5 are in our black gemstone beads collection, and hardness, weight and surface matter as much as color when you choose between them.

Black Beads at a Glance

Black Onyx: Even, Glossy and Classic

Onyx is chalcedony, the fine-grained form of quartz that also gives us agate and carnelian. In the strict mineral sense, onyx is chalcedony with straight, parallel bands, often black and white. In the bead trade, black onyx is evenly black chalcedony.

How to recognize it: a uniform, deep jet black with no pattern, lines or sparkle, and a polish that looks the same from bead to bead. At 6.5 to 7 it is hard enough for rings and bracelets. Matte onyx can turn dull and dusty over time; a drop of mineral oil brings it back, as we explain in how to revitalize matte stones. Shop onyx beads in smooth, matte and faceted cuts.

Obsidian: Volcanic Glass

Obsidian forms when silica-rich lava cools so quickly that crystals have no time to grow. The result is a glass with no crystal structure, and like any glass it breaks with a conchoidal fracture: smooth, curved, shell-shaped surfaces with very sharp edges, which made it a favorite for stone blades. At 5 to 5.5 it is the softest of the 5 stones here.

How to recognize it: a bright, wet-looking glassy shine, and at a thin edge held up to a strong light, a faint smoky translucence. If a bead has a chip near the drill hole, the chip will show that curved, shell-like break. Many obsidians carry a sheen or pattern: rainbow obsidian flashes bands of color, golden sheen obsidian and silver sheen obsidian glow from tiny aligned gas bubbles, and snowflake obsidian is speckled with white crystals. Like any glass, it can chip if knocked. For more on its varieties, see our guide to obsidian, or shop obsidian beads.

Black Tourmaline: Schorl

Black tourmaline is schorl, the iron-rich and most common member of the tourmaline group of boron silicates. It grows as long, prism-shaped crystals with fine grooves, called striations, running along their length. It breaks with an uneven to conchoidal fracture rather than splitting. At 7 to 7.5 it is the hardest of the 5, and it is denser than onyx or obsidian.

How to recognize it: look closely under good light and you will usually see traces of the crystal's structure: faint parallel lines, tiny pits or fractures, and a luster that is glassy in some spots and duller in others. Some strands show small gray, brown or rusty inclusions. That slight unevenness is the easiest way to tell it from onyx, which is perfectly uniform. Shop tourmaline beads for black tourmaline in smooth, matte, faceted and chip shapes.

Hematite: Metallic and Heavy

Hematite is an iron oxide and the main ore of iron, and it is by far the heaviest of the 5: a strand of real hematite weighs about twice as much as the same strand of onyx. Polished, it has a true metallic luster in a dark gunmetal gray. Much of the "hematite" sold in the bead trade is hematine, a man-made material based on iron oxide, and magnetic strands are always man-made.

How to recognize it: the weight gives it away immediately, along with the cold, mirror-like metallic surface. Real hematite leaves a reddish brown streak when rubbed on unglazed porcelain, and a fridge magnet barely registers it; magnetic hematine snaps to a magnet and to other beads. Hematite is brittle, so a dropped strand can crack, and its weight adds up fast in a long necklace (see properly weighting jewelry designs). Small 2 mm to 4 mm hematite beads make shiny spacers.

Lava: Light, Porous Basalt

Lava beads are cut from basalt, the most common volcanic rock on Earth. Gas trapped in the molten rock left bubbles as it cooled, and those bubbles are the pores you see on every bead. They make lava very light for its size and give it a rough, matte surface.

How to recognize it: nothing else on this list is pitted all over or as light. A drop of water disappears into the pores. That same porosity is why lava is the classic bead for essential oil diffuser bracelets; our tutorial on how to make a lava bead diffuser bracelet walks through one. The rough surface is abrasive, so string it on thicker cord (see our guide to elastic cords), and rinse and dry it fully if lotion builds up. Shop lava beads.

Other Black Beads Worth Knowing

Black Spinel

Spinel is a magnesium aluminum oxide, and at 8 on the Mohs scale it is harder than any stone above. Black spinel is usually cut in small faceted sizes with a bright, glassy sparkle. Shop spinel beads.

Larvikite

Larvikite, sold as black labradorite, is an igneous rock from Norway made mostly of feldspar crystals. It is dark gray to black, and as it moves the crystals flash silvery blue. Hardness is 6 to 6.5. Shop larvikite beads.

Shungite

Shungite is a carbon-rich rock from Karelia in northwest Russia: soft (about 3.5 to 4), light, black to steel gray with a slightly metallic cast, and electrically conductive. See smooth round shungite beads.

Black Jasper

Jasper is opaque, patterned chalcedony, and the black varieties are usually patterned rather than solid: black silver leaf jasper (6.5 to 7) shows silvery gray leaf-like markings, while black Picasso jasper, with fine white and gray lines, is often a softer marble sold as jasper.

How to Tell Black Beads Apart

A few simple checks identify most loose black beads. Test anything that could mark a bead on a spare.

• Weight: compare same-size beads in your palm. Hematite is unmistakably heavy, tourmaline dense, onyx and obsidian moderate, and lava almost hollow.
• Magnet: a strong pull to an ordinary magnet means magnetic hematine. Real hematite barely reacts, though some non-magnetic hematine exists too.
• Temperature: touch the bead to your lip. Hematite and tourmaline feel cold and stay cool for a moment; lava, full of air, feels the least cold; plastic feels warm right away.
• Luster: metallic means hematite; bright and glassy, sometimes with a sheen, suggests obsidian; even and glossy suggests onyx; glassy with patchy dull spots and fine lines suggests tourmaline; matte and pitted is lava.
• Hardness: onyx and tourmaline will scratch ordinary window glass, while obsidian barely marks it. Our guide to the Mohs hardness scale explains the numbers.
• Porosity: a drop of water sinks into lava and beads up on everything else.
• Streak: rub a spare bead on the unglazed back of a ceramic tile. A reddish brown streak points to real hematite.

Frequently Asked Questions

What is the difference between onyx and obsidian?

Onyx is chalcedony, a fine-grained quartz (6.5 to 7) with a very even, glossy finish. Obsidian is volcanic glass, softer at 5 to 5.5, with a brighter shine and often a sheen.

How can you tell if hematite is real?

Real hematite is very heavy, barely reacts to a magnet, and leaves a reddish brown streak on unglazed porcelain. Beads that snap to a magnet are man-made hematine.

Which black gemstone is the hardest?

Of these 5, black tourmaline at 7 to 7.5. Black spinel is harder still at 8.

Why does black tourmaline have lines on it?

Tourmaline crystals grow with fine lengthwise grooves called striations, and polished beads often keep faint traces of them. They are part of the stone, not damage.

Why are lava beads used with essential oils?

Lava is porous, so a drop of oil soaks into the pores instead of running off.

Shop Black Beads

Browse our full black beads collection, or go straight to onyx, tourmaline and hematite. For another black gem with a long past, read the history of jet.