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.
Key Facts
- Mohs hardness 6.5-7 – same as Quartz (since chemically it IS quartz).
- Specific gravity 2.55-2.65 – same as Quartz.
- NOT a separate mineral species – a variety of chalcedony, which is a variety of quartz.
- Banding forms during slow silica precipitation in cavities; layers reflect chemistry shifts in groundwater.
- Idar-Oberstein (Germany) is the historical center of agate carving; modern supply mostly from Brazil and Indonesia.
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.
Found at these Localities
- Maharashtra Deccan Traprock Zeolites (马哈拉施特拉德干玄武岩沸石产地)
- Inner Mongolia (内蒙古)
- Eastern Brazilian Pegmatite Province (巴西东部伟晶岩省)
- Oumjrane Mining Area (奥姆贾兰矿区)
- Bou Azzer District (布·阿扎尔钴矿区)
- Imiter Mine (伊米泰尔银矿)
- Rapid Creek (Yukon) (育空地区急流溪磷酸盐产地)
- Tri-State Mining District (Joplin) (三州矿区(乔普林))
- Swiss Alps (Alpine-Cleft Province) (瑞士阿尔卑斯高山裂隙矿物产地)
- Trimouns Talc Mine (特里穆滑石矿(法国))
- Siegerland District (西格兰铁矿区)
- Příbram (普日布拉姆银矿)
- Cornwall Mining District (康沃尔矿区)
- Ural Emerald Mines (乌拉尔祖母绿矿)
- Kongsberg (康斯堡银矿)
- Kharan, Balochistan (卡兰板钛矿产地)
- Kalgoorlie–Boulder (卡尔古利金碲矿)
- Săcărâmb (Nagyág) (萨卡拉姆布金碲矿)
- Panasqueira (帕纳斯凯拉钨矿)
- Cavradi Gorge (卡瓦拉迪峡谷)
- Volyn (Volodarsk-Volynskii) (沃伦伟晶岩区)
- Skardu / Shigar Valley (斯卡都/希加尔峡谷)
- Madagascar Pegmatites (Sahatany / Antsirabe) (马达加斯加伟晶岩区)
- Sweet Home Mine (甜蜜之家矿)
- Ouro Preto Region (欧鲁普雷图矿区)
- Llallagua (Siglo XX) (亚亚瓜矿)
- Erongo Mountains (埃龙戈山)
- Heqing Cu-Ag-Pb-Zn District (鹤庆铜银铅锌矿区)
- Yangla Copper Mine (羊拉铜矿)
- Xinglonggou (Fushun Amber Beds) (兴隆沟琥珀产地(抚顺))
- Shimen Realgar-Orpiment Mine (石门雄黄雌黄矿)
- Xiaoqinling Gold Field (小秦岭金矿田)
- Ying Silver Mine (银矿(豫西银多金属矿带))
- Erbutu Molybdenum Mine (二八图钼矿)
- Dachang Tin-Polymetallic Field (大厂锡多金属矿田)
- Yaogangxian Mine (瑶岗仙矿)
- Hubei (湖北)
- Sichuan (四川)
- Hunan (湖南)
Available Products of Agate
12 available specimens
Varieties of Agate
Agate is a parent species — the following named varieties differ in color or chemistry but share the same fundamental mineralogy.
- Blue Lace Agate (u84ddu7eb9u739bu7459)pale blue lacy bandsPale-blue lace-banded agate variety, primarily from Namibia.
- Fire Agate (u706bu739bu7459)iridescent rainbow over brownIridescent fire-pattern chalcedony from Mexico/SW USA.
- Moss Agate (u82d4u7eb9u739bu7459)green dendrites in clear chalcedonyChalcedony with green dendritic mineral inclusions resembling moss.
