Locality - Bity, Madagascar Size – 165 x 114 x 80mm Weight – 1350g
This Spiny Desert agate geode displays exceptional aesthetics with an open central vug filled with lustrous, clear, sharply terminated, amethyst-tinted quartz crystals. Some of the crystals contain unique black needle-like inclusions which may be goethite. The back of the piece has an unusual coral-like appearance and is riddled with small dimples. Overall, this large natural specimen has excellent composition and an attractive display face, ideal as a centerpiece or for the collectors cabinet.
Agate is a variety of chalcedony, recognised by its distinctively fibrous banding patterns. This banding is caused by periodic changes in the translucency within its substance, and is categorized into two different types; the typically seen wall-lining banding and the less common horizontal banding. Many agates originate in cavities of molten rock where gas bubbles trapped in solidifying lava are replaced with alkali and silica bearing solutions. Whilst agates are typically grey or brown, they can be found in an infinite and beautiful array of colours and patterns that make them desirable collectibles. Well-known varieties of agate include onyx, sardonyx, moss agate, blue ace agate, turritella agate, snakeskin agate and fire agate, though there are many more.
Agate in History
The name 'agate' originates from the locality at which it was found, the banks of the river 'Achates', where it was discovered in 400BC by the Greek philosopher Theophrastus. This gem was mentioned in the Bible as one of the 'stones of fire', and according to Pliny the Elder, agate was believed to make one agreeable and persuasive when worn. Agate has been prized since antiquity and has been used extensively in carvings, jewellery and tools in cultures worldwide.
A note on Fakes, Treatments & Misrepresentations
Since common agate is porous and typically found in greyish colours, many pieces are dyed vibrant colours to make them more saleable. These can be easily recognised by their unnatural neon colours, typically pink or blue, and are often seen at gift shops. The dye used is quite weak, so if a dyed piece is left in water long enough the colour will run out of the stone. Onyx is almost always a dyed agate. Agates are often mistaken for jasper, and vice versa, and the classifications of the two are widely disputed.