瑪瑙

Agate is a banded variety of chalcedony – itself a cryptocrystalline (microscopic-crystal) form of quartz. Chemically it is the same SiO2 as macrocrystalline quartz, but the crystals are too small to see without a microscope, giving the rock a smooth waxy texture. Banding patterns – parallel, concentric, fortification, eye-shaped, moss inclusions – are agate's signature. It is not technically a distinct mineral species but a textural variety; it is included in the encyclopedia because collectors treat it as an independent category and it appears on hundreds of shop products.

Notable Varieties

• Banded (classic – parallel/concentric layers)
• Moss agate (chlorite or manganese inclusions form moss-like patterns)
• Botryoidal / Grape agate (Indonesia – "purple grape" clusters)
• Lake Superior agate (USA – iron-red banding)
• Brazilian agate (large geodes; commercial supply)
• Fortification agate (sharp angular bands)
• Eye agate (concentric bullseye patterns)

The Chinese Angle

Liaoning and Inner Mongolia produce significant Chinese agate, typically as banded nodules and fortification varieties. Aershan in Inner Mongolia is a notable Chinese locality. However, most international agate trade still flows from Brazil, Indonesia (grape agate), Lake Superior, and Madagascar. Chinese agate carving has a long tradition (jade-style techniques applied to agate) and produces signature ornamental pieces.

@misc{mmb_agate,
 author = {{MyMineralBox Editorial Team}},
 title = {{Agate}},
 year = {2026},
 publisher = {My Mineral Box},
 url = {https://mymineralbox.com/mineral-encyclopedia/minerals/agate/},
 urldate = {2026-05-23}
}