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Floater Agate
Synonyms: Floater, suspended-center agate, suspended-banding agate
Characteristic features: Regions of chalcedony banding surrounded by thick bands of coarse quartz crystals; a single region of chalcedony banding surrounded by quartz may exist at the center of a specimen, or banded chalcedony sections may alternate with layers of coarse quartz crystals
Rarity: Floater agates are fairly common in the entire Lake Superior region, but are not quite as abundant as fortification agates
Description: While the name “floater agate” was invented by collectors and is not a scientific term, there is no better way to describe the “islands” of banded chalcedony that seem to float in masses of quartz in these agates. While they all contain ample amounts of chalcedony and quartz, there are two types of floater agates. Some consist of a single central mass of chalcedony surrounded by one body of quartz, while others consist of alternating regions of banded chalcedony and quartz, creating several “floating” bands. As chalcedony requires much more silica to form than macrocrystalline quartz, the varying amounts of each in a floater agate reflect dramatic rises and falls in the amount of available silica during the agate’s formation. These wild swings in silica content led to the formation of large individual quartz crystals within the macrocrystalline quartz, creating jagged boundaries between the chalcedony and quartz layers. When the chalcedony resumed forming, it filled in around these crystal points, preserving their shapes. These unique jagged borders are found in almost all specimens
Identification: Floater agates are a variation of fortification agates (page 23), and as such they contain the common band-within-a-band agate structure. But unlike classic fortification agates, some of the bands within floaters are composed entirely of coarse macrocrystalline quartz. This is the first thing to look for when identifying these agates. The macrocrystalline quartz is always evident in both floater agate types, and the quartz layers are typically quite thick and noticeably more plentiful in floater agates than in fortification agates. The banded quartz agate (page 41) is the only agate type you’re likely to easily mistake for a floater agate, but that’s only likely if a specimen is nearly whole and doesn’t show much of its interior pattern. Banded quartz agates contain little to no interior chalcedony banding and instead exhibit a large central mass of macrocrystalline quartz, so if only a small, shallow portion of an agate’s interior is visible and only macrocrystalline quartz can be seen, it could be a banded quartz agate, or it could be a floater agate with the chalcedony bands hidden deeper within. If there are few other clues, only cutting the agate will reveal its identity.
Collectibility: Normally just called “floaters” by collectors, floater agates are often visually interesting and can be very collectible when colorful. But as with any variety of Lake Superior agate, many collectors dislike floaters that contain excessive amounts of macrocrystalline quartz. However, with the right balance of chalcedony banding, macrocrystalline quartz thickness, and vivid coloration, floaters can be very desirable and valuable.
Compare & Contrast:
Banded Quartz Agate: more quartz and less chalcedony banding
Agate Geode: Can exhibit quartz bands, but has a hollow center
Fortification Agate: No large quartz bands
Skip-an-Atom Agate: Quartz bands are opaque and grayish blue
Where to begin looking: As one of the most common types of agate, floaters can be found anywhere in the region. Gravel pits near Cloquet, Minnesota, are very lucrative, as is Ontario’s Lake Superior shoreline.
