Dictionary.net

• A mineral occurring as an aggregation of minute scales having an olive-green color and pearly luster. It is a hydrous silicate of aluminia and iron.

2010 - New Age Dictionary Database
By Oddity Software

• A mineral occurring as an aggregation of minute scales having an olive-green color and pearly luster. It is a hydrous silicate of aluminia and iron.

1913 - Webster's Revised Unabridged Dictionary
By Noah Webster.