Tandon Gems

Stone guides.

What each stone is, how hard it is, how it is cut for beads, and what to check on a strand.

A strand of gray labradorite beads showing blue flashes under a point light.Stone guides

What is labradorite and why does it flash

Labradorite is a plagioclase feldspar whose blue to gold flash, called labradorescence, comes from light bouncing between thin internal layers. To judge a strand, tilt it under one point light and count how many beads show face-up color. More even, face-filling flashes across more beads signals a stronger strand for stringing.

September 5, 2026 · Anish Tandon
A strand of Ethiopian Welo opal rondelle beads showing play of color.Stone guides

Why Ethiopian Welo opal is cheaper than Australian opal

Ethiopian Welo opal, found in 2008 in Ethiopia's Wollo province, is abundant and cut in high volume, so bead strands with real play-of-color usually cost far less than Australian material. White body opal looks opaque to milky; crystal body is transparent. Judge fire by flashes of green, orange and blue from several angles across multiple beads.

September 5, 2026 · Anish Tandon
A close photo of multi-color Umba sapphire bead strands showing pink, green, yellow and purple tones.Stone guides

What is Umba sapphire and are multi sapphire beads real sapphire

Umba sapphire is natural corundum from Tanzania's Umba River valley, known for yielding pinks, oranges, greens and purples from one deposit. Multi sapphire beads are real sapphire, the same mineral as blue sapphire. All colors except red are sapphire, with Mohs 9 hardness. That's why a single strand can show a full, natural color mix.

September 5, 2026 · Anish Tandon
A close-up of small faceted chrome diopside rondelle beads showing bright grass green color.Stone guides

Choose chrome diopside strands by size, shape, and what to avoid

Pick 3 mm faceted rondelles for the brightest chrome green. 4 mm can work if the beads are shallow and well cut; 5 mm risks going near black. Choose shallow profiles like small rondelles or thin pears to keep color rich. In 3 to 5 mm, avoid tall chunky cuts, uneven drilling, and strands that look yellowish like peridot or show bubbles like glass.

February 20, 2025 · Anish Tandon
A strand of blue chalcedony beads glowing softly against a white background.Stone guides

How to grade translucency in blue and lavender chalcedony beads

Use two quick bench tests. Backlight a single bead with a phone flashlight and sort strands into High, Medium or Low glow by how much light blooms through the body. Then place one bead over printed text; if letters stay readable through the center, it's higher translucency. Choose smooth ovals, pears and teardrops to maximize that inner glow.

May 14, 2024 · Anish Tandon