Which sizes hold blue flash best?
Blue flash shows up most reliably on beads 4 mm and larger. Micro sizes can flash, but they demand a precise viewing angle and careful cutting to line up the internal layers. Larger faces make the effect easier to see and keep. On our trays, coins, cushions, rectangles, pears, and pyramids tend to show the strongest blue when the strand is well cut.
Which bead shapes show the strongest flash?
Broad, flat faces and long facet windows make the sheen easier to catch. Coins, cushions, rectangles, and pyramids give you that face. Pears and marquise work beautifully in earrings because they swing, constantly re-finding the angle. Faceted rondelles can flash well when the cutting windows are aligned, but tiny ones demand more angle hunting.
Orientation matters. Cutters aim the faces relative to the sheen plane so the flash turns on with a slight tilt. That is why two similar shapes can behave differently. We cut rainbow moonstone in marquise, pear, and pyramid, and we watch for shapes that hold flash across most beads.
How should I test rainbow moonstone under indoor light?
Use a single warm white lamp. Avoid multi-source glare. Hold the strand in front of the lamp, then tilt slightly and rotate bead by bead. Watch for a crisp blue that switches on and off as you move, not a vague milkiness.
Walk the strand slowly across the beam and roll the beads between your fingers. Mark the most responsive beads so you can feature them in the front row of a necklace or a pair of earrings. Record a short clip for your build notes.
How should I test it in daylight?
Stand in open shade or by a bright north window. Avoid direct sun that washes out the sheen. Repeat the slight tilt and slow rotation. Compare which beads hold color both indoors and in daylight, and plan your layout around the keepers.
Handle gently during testing. Rainbow moonstone is Mohs 6 to 6.5 with perfect cleavage, so hard knocks can split a bead. Warm soapy water only for cleaning. No ultrasonic or steam.
What should I look for across a whole strand?
Top grade shows strong blue across most beads. A strand with only a few blue beads and the rest chalky sits at the bottom. Ask for lamp and daylight photos or video; we shoot actual strands unless marked representative on our shop.
Quick ID check for look-alikes: opalite glass glows the same from every angle and may show bubbles. True feldspar sheen switches on and off as you tilt. If the glow never blinks, it is not rainbow moonstone.
How many 6 mm beads do you need
For a 7.5 inch bracelet, the beaded run is about 6 inches, so 6 mm rounds or rondelles use about 25 beads. For an 18 inch necklace, plan about 70 beads of 6 mm. A 16 inch choker uses about 61 beads of 6 mm.
A 15 to 16 inch strand of 6 mm rondelles typically has about 65 to 70 beads. Two such strands comfortably cover a longer necklace. Knotting between beads adds about 1 mm per knot, so adjust counts when you plan to knot.
How do I string to keep the flash visible?
Give flashy faces some breathing room. Light spacers or occasional micro rondelles prevent crowding so facets can catch light. In graduated sets of pears, keep points aligned in one direction for a clean rhythm and consistent tilt angles.
Feature the strongest beads front and center. For rondelles, alternate slightly taller beads near flashy ones to stagger facet heights. On flat cuts like rectangles, avoid tight curves at the clasp area where faces turn away from light.