 |
|
|
Cookeite (pronounced Cook-ite) is an uncommon member of the Chlorite group, and is best known for its occurrence in granite pegmatites associated with Tourmaline, where it often forms as a growth layer upon the Tourmaline. Cookeite is named in honor of Josiah Parsons Cooke Jr. (1827-1894), a Harvard University scientist who was instrumental in the measurement of atomic weights. |
|
|
Chemical Formula |
LiAl5Si3O10(OH)8 |
|
Composition |
Basic lithium magnesium aluminum silicate |
|
Color |
White, beige, yellow, orange, green, light blue, light brown, light pink |
|
Streak |
white |
|
Hardness |
2.5 |
|
Crystal System |
Monoclinic |
Crystal Forms
and Aggregates |
Crystals, which are always small, are in tabular pseudohexagonal form. Most often in radiating and botryoidal aggregates, as ball-shaped spheres, and in micaceous crusts, flakes, and small rosettes.
|
|
Transparency |
Translucent |
|
Specific Gravity |
2.58 - 2.69 |
|
Luster |
Pearly, waxy |
|
Cleavage |
1,1 |
|
Fracture |
Uneven |
|
Tenacity |
Flexible but not elastic. |
|
Other ID Marks |
May have a slightly greasy feel. |
|
In Group |
Silicates; Phyllosilicates; Chlorite Group |
|
Striking Features |
Crystal habits, localities, and mineral associations |
| Environment |
As an alteration mineral in lithium-rich granite pegmatites.
|
| Rock Type |
Igneous |
|
Popularity (1-4)
|
3 |
|
Prevalence (1-3)
|
3 |
|
Demand (1-3) |
2 |
|
|
 |
|
|
|
|
Cookeite is best known from the pegmatite quarries in Oxford Co., Maine. Specific localities there include Mt. Rubellite, Hebron; Mt Mica, Paris; Plumbago Mountain, Newry; the Tamminen Quarry, Greenwood; and the Bennett Quarry, Buckfield. Cookeite also comes from the Gillette Quarry, Haddam; and at the Strickland Quarry, Portland; both in Middlesex Co., Connecticut.
Some of the best bluish and greenish Cookeite, in interesting ball aggregates with Quartz, comes from Saline Co., Arkansas, especially at the
Stand-on-Your-Head mine in Bland. Good Cookeite also comes from the Tourmaline mines around Pala, San Diego Co., California; as well as the Tourmaline mines of of Minas Gerais, Brazil, especially at Conselheiro Pena in the Doce valley.
|
Muscovite and other micas - Are more elastic.
Talc - Softer (1).
|
|
|
|
|
|
|
|
Have a question about Cookeite? Visit our Q&A Community and ask the experts!
|
|
|
|
Let us know how we can update this page
(Click for more details)
|
|
We strive for accurate content and locality information. If you feel any of the content is incorrect, or if you feel we are missing vital locality information, please fill out the form below so we can update the site. If you are requesting a locality be added, please only include significant locality occurences for the mineral.
|
 |
| |
|
|
|
|
|
|
|
