TREMOLITE
Iowa Hill, Placer County, California
These specimens are from an occurrence within the historic Gold producing California “Mother Lode” district.  This occurrence is mentioned in “Minerals of California”, H. Pemberton, 1983, P. 398, where white slip-fiber asbestos, with fibers up to 8 inches in length, is reported to have been found at two claims in the vicinity of Iowa Hill, near Placerville.  The specimens listed below all exhibit the elongated, white, fibers characteristic of this asbestiform mineral.  Items A. and B. are good for reference collection of asbestiform minerals, and any of the larger specimens are quite suitable for display in a collection of asbestiform minerals.  The pale greenish mineral seen in some of the photos is pale green Serpentine, included with white Tremolite fibers
 

RIEBECKITE Var. Crocidolite
Griqualand West, Northern Cape Province, South Africa
From “Gems, Minerals, and Rocks in Southern Africa”, by J. McIver, 1966, “Oriented silky fibers of Riebeckite are known as Crocidolite asbestos.  Crocidolite occurs only in certain banded ironstone formations and, although large deposits are known in South Africa, Crocidolite asbestos is rare in other parts of the world.  The only other large deposits are found in Australia.”  The color of the individual, silky luster, needle-like Crocidolite fibers on these  specimens is a light greenish-gray and, in the areas where the mineral is compact the color is a more intense, darker greenish-gray.  Each specimen consists of a vein section of compact, silky luster, needle-like Crocidolite, bordered on the top and bottom of the vein with a small amount of matrix.  Note that these specimens are not recently mined – they are from a collection, recently obtained from a source in South Africa. 


 

ACTINOLITE (Amianthus) inclusions in QUARTZ
Gotthard Pass, Switzerland
Amianthus is the older European name used to describe acicular Actinolite found in some of the Alpine cleft deposits.  This specimen is from the F. Marshall collection, probably collected in the early to mid-1980’s.  See also item MI-1225 on Page 6 of this list – Actinolite (Byssolite).  This specimen consists of a group of more than 10 intergrown Quartz crystals, without matrix.  The two largest Quartz crystals measure 1 1/4” and 1 1/2” in length, and the tiny gray-green hair-like needles of included Actinolite (Amianthus) give the Quartz crystals a pale greenish appearance, especially near the center of the group.  The base of the specimen is micro crystallized Quartz (no rock matrix).  Attractive!
Specimen size:  2 3/4” X 2” across, X 1 1/4” thick.
Order Item MI-1203
Price:  55.00 SOLD

RIEBECKITE inclusions in DANBURITE
Alto Chapare District, Chapare Province, Cochabamba Department, Bolivia
Blue-gray, hair-like Riebeckite inclusions within the Danburite crystals (ID by x-ray analysis) have tinted the Danburite crystals a light smoky gray color.  Specimens are very sharp, complete double terminated single crystals of Danburite with pale smoky gray color hair-like inclusions of Riebeckite, without matrix. 

 

RIEBECKITE Var. Crocidolite “Tigereye”
Asbestos Mountains, North of the Orange River, West Griqualand, Northern Cape Province, Republic of South Africa
Tigereye is the name given by lapidaries to silicified Crocidolite.  The material is very tough and compact, rather than hairy or fibrous, typical of Crocidolite from other localities.  The variation in the color of the South African Tigereye ranges from golden to brown, blue-golden (known in gem cutting circles as “Hawk’s Eye” because of the blue color), to brick red, and the latter seems to be the rarest.   Items A and B are blue-golden in color, and item C is red Tigereye, actually a brick red color.  Items D through G are the more typical, best known golden color Tigereye with light chocolate brown colored bands.  All are unpolished slices with excellent chatoyancy, suitable for reference collection of asbestiform minerals, or for fashioning into cabochons.  These specimens were collected ~ 15 to 20 years ago, from a locality which is no longer in production.  Specimens are not sold by the gram – the gram weights are given simply as a measure of size.
 

E.

F.

G.

RIEBECKITE Var. Crocidolite (Pietersite)
Outjo, Damaraland District, Kuene Region, Namibia, East Africa
Pietersite was first discovered by Sid Pieters in 1962.  He registered the find in the mineral records of Great Britain.  The news of the new find was published in 1964, and the mineral was named Pietersite in his honor.   More recently, Pietersite has been found to be a variety of Riebeckite.   Pietersite is extremely rare and has been found in two locations world-wide: Namibia, East Africa and more recently in Hunan, China.  The price of Pietersite has risen in the past several years due to the closure of the Chinese mine, limited production from the mine in Namibia, an increase in demand, and difficulties in export.  When Pietersite is seen for sale, it has usually been cut into cabochons, and the color is varied from blue to greenish, red-brown, or golden-brown.  We were very fortunate to be able to acquire specimens of the pure blue color, with each of the largest specimens exhibiting a small amount of golden-brown streaking and excellent chatoyancy. Lapidaries refer to the blue Pietersite as “Hawk’s Eye” or “Eagle’s Eye”.  All specimens exhibit the characteristic asbestiform habit with silky luster. Items A., B., C., and H. each have a very small amount of matrix present, and the remaining specimens are matrix-free.  The weights of the two largest specimens are given as a measure of size – the specimens are not sold by the gram.  The white mineral seen in the photos of items E. and F. is a very thin secondary deposition of caliche.  This could be removed, if desired, with dilute HCl.






 

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