Agate /ˈæɡət/ is a microcrystalline variety o silica, chiefly chalcedony, characterised bi its fineness o grain an brichtness o colour. Altho agates mey be foond in various kinds o rock, thay are classically associatit wi volcanic rocks an can be common in certain metamorphic rocks.[1]

Agate
Agate banded 750pix.jpg
Bandit agate (agate-lik onyx); the specimen is 2.5 cm (1 inch) wide
General
CategoryQuartz variety
Formula
(repeatin unit)
SiO2 silicon dioxide
Creestal seestemRhombohedral Microcrystalline
Identification
ColourWhite tae grey, licht blue, orange tae reid, black. bandit
Creestal habitCryptocrystalline silica
CleavageNone
FracturConchoidal wi very sharp edges.
Mohs scale haurdness6.5–7
SkinkleWaxy
StreakWhite
DiaphaneityTranslucent
Speceefic gravity2.58–2.64
Refractive index1.530–1.540
Birefringenceup to +0.004 (B-G)
PleochroismAbsent

ReferencesEedit

  1. Donald W. Hyndman, David D. Alt (2002). Roadside Geology of Oregon (18th ed.). Missoula, Montana: Mountain Press Publishing Company. p. 286. ISBN 0-87842-063-0.