Category: Gem Notes

JEREMEJEVITE

INTRODUCTION Jeremejevite is a mineral species with the formula,  Al6B5O15(OH,F)3. It is pronounced by replacing the “J” with “Y” so phonetically, it would be “yeremeyevite.” It was first discovered in 1883 on Mt. Soktuj in East…

Rhodochrosite

Rhodochrosite has been used as an ornamental material for carvings, beads and inlays due to its low hardness, for a very long time. Beautiful pink color contrasting with white banding in massive form is the…

Iolite

INTRODUCTION Iolite is the trade name for gem quality cordierite, a mineral species in the orthorhombic system, with the formula, (Mg,Fe)2AL4Si5O18. Cordierite has been known for hundreds of years and was named in 1813 after…

A Sapphire’s Secret

INTRODUCTION At Lotus Gemology, our Bangkok-based gem testing laboratory, we only test for two types of stones: corundum (ruby & sapphire) and spinel. As a result, we often get parcels of stones with similar attributes. This…

Chrysoberyl

Introduction Chrysoberyl, BeAl2O4, is a mineral species with well-known varieties, namely alexandrite and chrysoberyl cat’s eye. Much has been written about chrysoberyl’s varieties, so this gem note is intended to focus on the transparent faceted material. Chrysoberyl…

Hackmanite

Introduction Hackmanite, Na8Al6Si6O24(Cl2,S), is the rare variety of the mineral species sodalite. Sodalite is a translucent to opaque, dark blue to violet-blue material that is used for jewelry purposes, typically fashioned as cabochons or beads, while…

Clinohumite

Introduction Clinohumite, (Mg,Fe)9(SiO4)4(F,OH)2, is a mineral species in the humite group which also includes humite, chondrodite, and norbergite. These species are easily confused with each other as they have similar properties that often overlap. The relative…

Kornerupine

Introduction Kornerupine is a mineral species with the formula Mg3Al6(Si,Al,B)5O21(OH). It crystallizes in the orthorhombic system. The minerals kornerupine and prismatine were once considered to be the same mineral, but microprobe analysis proved that the two…

Andalusite

Introduction Andalusite is a mineral species crystallizing in the orthorhombic system with the formula Al2SiO5. Two other gem species, namely kyanite and sillimanite, have the same chemical composition as andalusite but with different physical structures. All three form under different conditions of temperature and…

Diopside

Introduction Diopside is a mineral species crystallizing in the monoclinic crystal system with the formula CaMgSi2O6. It is the end member of a solid solution series to hedenbergite where the magnesium is replaced by iron, CaFeSi2O6. There are a few intermediate…