Ruby-in-Zoisite (Anyolite): properties, varieties and value factors

Key properties

Chemical formula	Zoisite Ca2Al3(SiO4)3(OH) with ruby Al2O3 and pargasite (amphibole)
Mohs hardness	6-7
Toughness	Fair to poor (zones of differing hardness, one perfect cleavage in the zoisite)
Refractive index	1.691-1.700
Birefringence	0.0080-0.0130
Optic character	Biaxial positive (zoisite component) (+)
Dispersion	0.0210
Specific gravity	3.30-3.45
Cleavage	Perfect in one direction in the zoisite component
Fracture	Uneven to conchoidal
Habit	Massive granular rock; ruby occurs as coarse prismatic crystals embedded in the zoisite
Lustre	Vitreous to dull (pargasite zones nearly metallic-dark); polish: Vitreous
UV fluorescence	Rock generally inert; individual ruby crystals may glow weak crimson-red in long-wave UV, though Longido rubies are often too iron-rich to fluoresce strongly.
Pleochroism	Not relevant on opaque ornamental material; transparent zoisite itself is strongly trichroic.
Cause of colour	Green of the zoisite from chromium/vanadium trace elements; red of the ruby from chromium; black from the pargasite amphibole.
Typical inclusions	Interlocking green zoisite groundmass with scattered red ruby crystals and black-to-dark-green pargasite stringers and patches
Stability	Stable to light and everyday chemicals; fuses under a jeweller's torch; zoisite attacked by hydrochloric and hydrofluoric acids.
Heat sensitivity	High - avoid the torch and rapid temperature changes
Care and cleaning	Warm soapy water and a soft brush are safe. Keep ultrasonic and steam cleaners away: the cleavage direction and the hardness contrasts make the rock crack-prone.
Availability	Limited but steady supply of ornamental rough from a single mining district; popular with carvers and bead makers.
Recognition	The tricolour look - spinach-green, crimson-red and black - is unmistakable once seen; no other common gem rock mixes opaque green with opaque red.

Varieties

Ruby-in-Zoisite (Anyolite)

Colour	spinach-green zoisite speckled and veined with red ruby crystals and black pargasite
Transparency	opaque
Clarity type	Not applicable - opaque ornamental rock
Phenomena	None
Appearance	A lively granular green stone interrupted by eye-catching red patches and short prismatic ruby sections, all laced with dark amphibole. Polishes to a waxy-vitreous sheen with the ruby spots taking the best polish.
Trade names	Anyolite • Tanganyika artstone • ruby zoisite
Misnomers	Sold simply as "zoisite", which overstates the case - it is a rock, not a gem variety of the zoisite species
Typical sizes	Beads and cabochons from a few carats up to plaques of hundreds of carats; sculpture rough occurs in blocks of many kilograms with ruby crystals to several centimetres.
Cutting styles	Cabochons, beads, boxes, spheres, carvings and figurines; almost never faceted except as tiny ruby-rich sections
Key separations	From unakite: unakite's pink is feldspar (granular, sparkle) and its green is epidote - both take a different texture, and unakite SG ~2.85-3.2 floats in heavy liquids above 3.1 where anyolite sinks. From ruby-in-fuchsite: fuchsite sparkles with a micaceous glitter and shows a green Cr absorption, with a much lower SG (~2.7-2.9). From green jade materials: jadeite/nephrite lack the red crystals and are tougher with fibrous texture.
Sources (localities)	Tanzania only: Longido area of the Umba valley (the classic deposits, worked since the 1950s) and the nearby Mundarara mine, with similar material in the Arusha region.
Availability	Steady from Tanzanian dealers in arcing supply; large carving rough increasingly scarce.
Market notes	Traded by the piece or the kilogram rather than by fine-gem standards; price hinges on the amount and contrast of red ruby. Recently publicised in the UK "Gem of Tanzania" fraud case, where a modest anyolite boulder was carried at an absurd book value.
Care notes	Set gently, avoid rough knocks, ultrasonic and steam. Warm soapy water only.
In short	Anyolite pairs opaque green zoisite with embedded red ruby crystals and black pargasite from a small corner of Tanzania. It is a carving and cabochon material whose value rides on colour contrast, not on gem quality.

Size (ct)	USD per carat	Tier	As of
1.00–20.00	$1.00 – $8.00	cabochon and bead material	2026-10-26

Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.

Sources

GIA gem encyclopedia · mindat.org · Wikipedia

Data compiled and fact-checked against gemmological literature, October 2026 (JDMIS gem reference). Properties are ranges accepted in gemmological practice; individual stones vary.

Key properties

Varieties

Ruby-in-Zoisite (Anyolite)

Sources

See also