GIA COLORED STONES COMPREHENSIVE
TESTBANK EXAM 2026 ENTIRE 1129
QUESTIONS AND PRECISE CORRECT
ANSWERS GRADED A+
⩥ Feldspars. Answer: The most widespread minerals on earth.
⩥ Why these gems need protection. Answer: They are relatively soft and
have cleavage in two directions, so they require protective settings.
⩥ Feldspar chemical basics. Answer: All feldspars contain aluminum,
oxygen, and silicon; potassium, sodium, and calcium vary and create
different feldspar species.
⩥ Feldspar classification tool. Answer: Triangle 'end-member' model:
potassium end-member (orthoclase/microcline), sodium end-member
(albite), calcium end-member (anorthite).
⩥ Two feldspar series. Answer: Alkali feldspar series (K-Na mix) and
plagioclase feldspar series (Na-Ca mix).
⩥ How labs name feldspar species. Answer: By physical properties,
chemistry, and whether a phenomenon is present; sometimes origin is
considered; phenomenon may be noted in report comments.
,⩥ How consumers recognize feldspars. Answer: Mostly by trade/variety
names based on phenomenon (e.g., moonstone, sunstone).
⩥ Moonstone. Answer: Variety name for any feldspar that shows
adularescence.
⩥ Adularescence. Answer: A billowy, rolling glow that moves across the
surface as viewing angle changes.
⩥ What causes moonstone adularescence. Answer: Scattering of light by
stacked, alternating feldspar mineral layers.
⩥ Adularia. Answer: Old name for moonstone; linked to Mt. Adular (St.
Gotthard), Switzerland—an early fine source.
⩥ Orthoclase moonstone composition. Answer: Intergrown orthoclase +
albite (both alkali feldspars) that separate into alternating layers during
cooling.
⩥ Other moonstone phenomena. Answer: Some show chatoyancy; rare
examples show four-rayed asterism.
, ⩥ Rainbow moonstone. Answer: A moonstone variety with multicolored
adularescence; actually a variety of labradorite (plagioclase feldspar).
⩥ Rainbow moonstone sources. Answer: Canada and Madagascar.
⩥ Finest moonstone look. Answer: Colorless, semitransparent to nearly
transparent; eye-clean; vivid blue adularescence.
⩥ Blue sheen. Answer: Trade term for vivid blue adularescence in top
moonstone.
⩥ Most common moonstone cut. Answer: Cabochon (best for showing
sheen).
⩥ Moonstone hardness. Answer: About 6 to 6.5.
⩥ Moonstone durability issue. Answer: Cleavage in two directions +
softness → better for pendants/earrings/pins than rings.
⩥ Moonstone carvings note. Answer: Softness makes it suitable for
cameos and 'man-in-the-moon' carvings; carving texture + sheen creates
lively effect.
TESTBANK EXAM 2026 ENTIRE 1129
QUESTIONS AND PRECISE CORRECT
ANSWERS GRADED A+
⩥ Feldspars. Answer: The most widespread minerals on earth.
⩥ Why these gems need protection. Answer: They are relatively soft and
have cleavage in two directions, so they require protective settings.
⩥ Feldspar chemical basics. Answer: All feldspars contain aluminum,
oxygen, and silicon; potassium, sodium, and calcium vary and create
different feldspar species.
⩥ Feldspar classification tool. Answer: Triangle 'end-member' model:
potassium end-member (orthoclase/microcline), sodium end-member
(albite), calcium end-member (anorthite).
⩥ Two feldspar series. Answer: Alkali feldspar series (K-Na mix) and
plagioclase feldspar series (Na-Ca mix).
⩥ How labs name feldspar species. Answer: By physical properties,
chemistry, and whether a phenomenon is present; sometimes origin is
considered; phenomenon may be noted in report comments.
,⩥ How consumers recognize feldspars. Answer: Mostly by trade/variety
names based on phenomenon (e.g., moonstone, sunstone).
⩥ Moonstone. Answer: Variety name for any feldspar that shows
adularescence.
⩥ Adularescence. Answer: A billowy, rolling glow that moves across the
surface as viewing angle changes.
⩥ What causes moonstone adularescence. Answer: Scattering of light by
stacked, alternating feldspar mineral layers.
⩥ Adularia. Answer: Old name for moonstone; linked to Mt. Adular (St.
Gotthard), Switzerland—an early fine source.
⩥ Orthoclase moonstone composition. Answer: Intergrown orthoclase +
albite (both alkali feldspars) that separate into alternating layers during
cooling.
⩥ Other moonstone phenomena. Answer: Some show chatoyancy; rare
examples show four-rayed asterism.
, ⩥ Rainbow moonstone. Answer: A moonstone variety with multicolored
adularescence; actually a variety of labradorite (plagioclase feldspar).
⩥ Rainbow moonstone sources. Answer: Canada and Madagascar.
⩥ Finest moonstone look. Answer: Colorless, semitransparent to nearly
transparent; eye-clean; vivid blue adularescence.
⩥ Blue sheen. Answer: Trade term for vivid blue adularescence in top
moonstone.
⩥ Most common moonstone cut. Answer: Cabochon (best for showing
sheen).
⩥ Moonstone hardness. Answer: About 6 to 6.5.
⩥ Moonstone durability issue. Answer: Cleavage in two directions +
softness → better for pendants/earrings/pins than rings.
⩥ Moonstone carvings note. Answer: Softness makes it suitable for
cameos and 'man-in-the-moon' carvings; carving texture + sheen creates
lively effect.
