Roseforge deals in two families, deliberately: vivid garnets and spinels — not a general coloured-stone inventory.
Garnet
Garnet is a broad family, not a single stone. It includes rhodolite (purplish-red to reddish-purple), almandine and pyrope (red), spessartine and hessonite (orange), and tsavorite and demantoid (green); colour-change varieties also occur. Most garnet on the market is untreated.
Spinel
Spinel is often mistaken for ruby — the Black Prince's Ruby, set in the Imperial State Crown, is spinel, not ruby. Its range spans red, pink, violet, lavender, grey, and cobalt blue. Spinel is typically untreated.
As minerals
Both minerals crystallise in the cubic system and are singly refractive — light travels through at one constant speed, whichever direction it takes. That rules out the angle-dependent colour shift seen in many doubly refractive stones. In garnet and spinel, the colour doesn't split or shift as the stone turns; it reads as one continuous field. It's a structural reason, not a sentimental one, for why both hold the vivid colour the way they do — depth that stays whole rather than splintering.
Both families are widely under-recognised relative to their range and rarity — part of why Roseforge specialises in them rather than carrying a broader, shallower stock.