Which one shows more color under a warm LED?
Moonstone, by a clear margin. Warm bulbs are heavy in the yellow and red end, and the blue scatter off the thin internal layers in rainbow moonstone pushes right through that, so the flash reads as a cool blue against the gray-white body.
Gray-body opal gets quieter. Its play-of-color depends on a spread of hues, and warm light thins out the blues and greens that usually dominate a gray base. You still see fire on the best beads, but the reds and oranges take over and the strand looks calmer than it did in the shop.
How does daylight LED change the comparison?
Daylight LED evens the field and often puts gray-body Australian opal ahead. The broad spectrum lets green, blue and red flashes fire at once, which is the effect people picture when they buy opal. Gray body gives those flashes a mid-tone backdrop, darker than white opal and easier on the eye than a bright base.
Moonstone under daylight LED looks cleaner but less dramatic. The blue is still there. It just competes with more light bouncing off the surface, so a chalky strand looks chalkier than it did under a warm bulb.
What shapes and sizes hold the flash indoors?
Opal needs surface area. A single flash patch can be a millimeter or two across, so a small faceted bead chops it into pieces you never see. Heishi discs and smooth ovals give the widest uninterrupted face, and smooth domes hold color better than lots of tiny facets.
Moonstone works at any size we cut it. Faceted rondelles at 3 to 4 mm still throw blue because the sheen comes from inside the bead and the facets only bounce it around. Coins, cushions and pyramids give the biggest single sheets of blue.
- Gray opal indoors: 8 mm heishi discs and smooth ovals first, faceted rondelles second.
- Moonstone indoors: 3 to 4 mm rondelles for even sparkle, coins and cushions for one strong flash.
- Pears and briolettes swing as they hang, which keeps moonstone lighting up while the wearer moves.
- Below about 4 mm, treat opal as a gray accent bead and let color come from somewhere else.
How do you judge either strand on the tray?
Count, then tilt. On opal, count the beads that flash against the ones that are plain gray potch; a good strand shows color on most beads. Look at the side of every heishi disc for a straight seam or a black backing, which tells you the bead is a doublet or triplet rather than solid material.
On moonstone, strong blue across most beads is top grade and a few blue beads with the rest chalky is the bottom. Tilt the strand under the light. Feldspar sheen switches off at certain angles, while opalite glass, the common look-alike, glows the same from every direction and shows tiny bubbles.
A water drop is the other quick check on Australian material. It sits on the surface instead of soaking in, because this opal is non-hydrophane and far more stable than porous types. We keep both stones on the stone guides if you want the grade names before you shop.
How many beads do you need for each length?
Plan on 1.5 inches for clasp and findings, which leaves about 6 inches of beaded run on a 7.5 inch bracelet and 16.5 inches on an 18 inch necklace. A 7.5 inch bracelet takes about 19 beads at 8 mm, about 25 at 6 mm and about 38 at 4 mm.
For necklaces, an 18 inch run takes about 52 beads at 8 mm, about 70 at 6 mm and about 104 at 4 mm. A 16 inch choker takes about 46 at 8 mm and about 61 at 6 mm. Knotting between beads adds roughly 1 mm per knot, so a knotted moonstone rope needs a second strand sooner than you expect.
Cutter strands run 13 to 16 inches, and 13 inch strands are common for faceted rondelles. One strand covers a bracelet or a choker. Two make a long necklace with beads left for earrings.
Which is easier to live with in a finished piece?
Opal is the softer of the two at Mohs 5.5 to 6.5, and gray-body Australian material is the most forgiving opal we handle. Warm water and a soft cloth are enough. Keep it away from ultrasonic cleaners, dry heat and fast temperature swings.
Moonstone is slightly harder at Mohs 6 to 6.5 but has perfect cleavage, so a hard knock can split a bead along a flat plane. We steer it toward earrings and necklaces rather than bracelets that take a beating. Warm soapy water only, no steam.
One more thing for the label. Opal is the October birthstone and moonstone the June one, and Australia named opal its national gemstone in 1993, which gives you something to write on the tag. Both stones ship by the strand from our shop.