Stone against stone, shape against shape, so you pick the right one before you buy.
Both are feldspars. Labradorite shows directional blue to gold flashes from a dark gray body. Moonstone shows a soft blue or white glow from a milky body. What many sellers call "rainbow moonstone" is actually white labradorite. We sort by body color first, then watch how the sheen turns on and off as we tilt the strand.
Half-moons give the most face for the least weight, then marquise, then pear, then oval. Sizes like 11x15 mm half-moons or 6x9 mm pears balance presence and comfort. By stone heft, zircon feels heaviest, then topaz, then tourmaline. At 3 mm per 8 inches: zircon 26 ct, topaz 20 ct, tourmaline 17 ct.
Pick sky blue topaz for the brightest pale blue and maximum sparkle, ideally in 3 to 4 mm faceted rondelles. For the lightest feel with a soft glow, choose blue chalcedony in small smooth rondelles or heishi. Aquamarine splits the difference for a natural March-birthstone look; 4 mm faceted rondelles read clean and refined.
Diamond-cut beads use a brilliant-style layout with larger, steeper facets for high flash, while micro-faceted beads pack many tiny, shallower facets for a fine shimmer. Facet designs show micro around 65 facets and brilliant styles about 58 to 69. At 2 mm micro you get silky sparkle and smooth feel; at 3 to 4 mm diamond-cut you get punchier flashes and a crisper hand. Use micro for drape, diamond-cut for pop.
Check color, matrix, hardness and care. Chrysocolla runs robin's-egg to sky blue-green with a waxy to glassy feel; shattuckite shows deeper royal blue in fibrous patches. Turquoise is more even blue to green with web-like matrix and a matte, opaque look. At drill holes, chrysocolla can look slightly translucent, shattuckite shows fibrous streaks, turquoise looks opaque. Pick turquoise for bracelets, either for necklaces.
At 3 to 4 mm, amethyst reads the most purple on bracelets and earrings. Iolite can shift slate or pale from some angles, and tanzanite tends to swing bluer at this size. To hold color, choose taller faceted rondelles or small ovals. Very flat heishi look lighter because there's less depth for the color to build.
Under most indoor light, rainbow moonstone shows more color. Its blue sheen comes alive under warm LED and stays readable down to 3 to 4 mm faceted rondelles. Gray-body Australian opal reads better under daylight LED, and it needs a broad flat face, so heishi discs and smooth ovals beat small rondelles. Tilt both strands before you buy.
The black fern-like markings are manganese and iron dendrites. Dendritic opal is common opal with a milky white body and no fire, while dendritic agate is glassier, more translucent chalcedony. For bold patterns, pick strands with crisp black branches on a clean white ground and motifs that span the face of each larger bead.