MICROCLINE
Specimen mic-13

Dims: 1-5/8" x 1-1/2" x 1-1/8"

Wt: 1.86 oz

Two Point Mine, Florissant, Teller Co., Colorado, U.S.A.

Though incomplete, this Microcline specimen is quite beautiful. It is of the variety Amazonite, the blue-green Microcline that is sometimes cut as a gemstone. The specimen consists of two crystals that form a penetration twin. The break that separated the specimen from its place of formation is angled so that at least 3 sides are incomplete, and a small part of each crystal's basal pinacoid termination is missing. The crystal and termination faces that still exist are clean and free of damage. The color is a uniform, deep blue-green.

Dims: 2-1/2" x 2-1/8" x 1-3/8"

Wt: 3.27 oz

Crystal Peak Mining Dist., Lake George, Park Co., Colorado, U.S.A.

This specimen is made up of two complete crystals of Microcline that are growing out of a larger, incomplete crystal. The incomplete crystal measures 1-1/8 x 1-1/2 in width and depth(its length is severely curtailed due to breakage). Both of the other crystals have collective dimensions of 1-1/2" x 1-1/8" x 3/4"; they are completely free of damage, and almost identical in structure, probably due to the fact that together they form a Carlsbad Twin. Their color is the obligatory beige of most orthoclase crystals.

Dims: 2.0" x 2.0" x 1.8" (5.1 x 5.1 x 4.6 cm)

Wt: 3.55 oz. (100.9 g)

Minas Gerais, Brazil

This specimen consists of a cluster of 5 partly intergrown Microcline crystals. These crystals range in size from 0.4 x 0.4 x 0.3" (1.0 x 1.0 x 0.8 cm) to 1.8 x 1.6 x 1.0" (4.6 x 4.1 x 2.0 cm) and show weathered but good triclinic prismatic form. Their edges are straight and mostly well-defined, and their faces are flat. However, there are many small hollows that extend into each crystal. These are definitely of natural origin and geometric in form. The crystals have a pale cream coloration and a dull, matte luster, and are completely opaque. There is no host rock present on the specimen, but several tiny muscovite books are clustered together where two of the crystals meet.

Dims: 3.0" x 2.3" x 1.9" (7.6 x 5.8 x 4.8 cm)

Wt: 3.56 oz. (101.1 g)

Minas Gerais, Brazil

This particular specimen reminds me more of albite than Microcline, actually. It consists of a confusing association of dozens of intergrown Microcline crystals. These crystals range in size from 2 x 2 x 2 mm to 1.0 x 0.7 x 0.6" (2.5 x 1.8 x 1.5 cm) and show so many oddities and inconsistencies in growth that it is difficult to tell one crystal from another. All have a creamy color and a dull-to-waxy luster, and are completely opaque. Among the profusion of intergrowth are many small books of muscovite and at least 7 hexagonal prismatic quartz crystals. The muscovites show definite hexgonal outlines and do not exceed 0.4" (1.0 cm) in diameter. The quartz crystals reach a maximum length of 0.8" (2.0 cm) and show excellent hexagonal prismatic form. They are colorless and have a bright, vitreous luster, and are transparent and very clear.

Dims: 1.7" x 1.2" x 1.2" (4.3 x 3.0 x 3.0 cm)

Wt: 1.72 oz. (48.8 g)

Crystal Peak Mining District, Lake George, Park County, Colorado, U.S.A.

A single Microcline crystal attached to a small amount of albite makes up this specimen. The Microcline is of the variety known as Amazonite, and shows its characteristic pale bluish-green coloration. The crystal is in excellent condition, showing no human-induced damage, and has excellent triclinic form; even its underside seems to have attempted to form a crystalline face! The Amazonite has a pearly luster and is translucent only along its edges, even in halogen light. The attached albite is heavily damaged and shows almost no discernable form.

Dims: 1.0 x 1.0 x 0.9" (2.5 x 2.5 x 2.3 cm)

Wt: 14.4 g

10 Percenter Mine, Teller County, Colorado, U.S.A.

This small thumbnail specimen consists of a single, undamaged crystal of the variety of Microcline that is known as Amazonite. It is in near-perfect condition and has excellent triclinic prismatic form, with well-defined edges and clean faces that show a pearly luster. The crystal appears to be doubly-terminated, but one termination is incomplete due to its intergrowth with some albite, most of which has been removed. It has the standard pale aqua-blue coloration that is common for Amazonite and shows dim translucence around its edges. Besides the attached albite, there is no host rock.

Dims: 2.2 x 1.6 x 1.6" (5.6 x 4.1 x 4.1 cm)

Wt: 4.9 oz. (138.4 g)

Crystal Park, Teller County, Colorado, U.S.A.

This simple hand specimen consists of a single monoclinic prismatic crystal of Amazonite, a blue-green variety of Microcline. It is in excellent condition, showing only a small amount of damage along one edge of its termination. Its form is exceptional- even the breakage at its base, where it broke prior to mining, has been partly healed. Its edges are well-defined and its faces are smooth and clean, possessing a pearly luster. Though showing some discoloration, it basically has a good, moderate bluish-green coloration. Some of its prism faces are a bit more rough in texture than others, and have a characteristically paler color. The clearer ones show the thin, pale lines that make up the standard visual texture of this material. There is no host rock present. This is one of the larger Amazonite crystals that I have seen available.

Dims: 1.5 x 1.3 x 1.2" (3.8 x 3.3 x 3.0 cm)

Wt: 1.99 oz. (56.5 g)

Sceptre Claims, Emerald Lake, Yukon Territory, Canada

The twinned Microcline crystal that makes up this specimen is incomplete, but the associated damage is old, having occurred prior to mining. Where intact, it has good triclinic prismatic form and shows strong evidence of Mannenbach-Baveno twinning One can easily see the twinning plane on the most complete face. Its edges are relatively well-defined and its faces are often striated but clean and possess a dull pearly luster. The crystal has a pale yellow color that may be due to rust-staining and is translucent, showing small areas of transparence in between the internal cleavage planes and assorted inclusions and internal fractures. A patch of tiny, dark brown crystals are present- I believe that they are calcites with very heavy iron inclusions. There is no host rock, and the piece is hot-glued onto a flat acrylic base.

Dims: 2.0 x 1.8 x 0.9" (5.1 x 4.6 x 2.3 cm)

Wt: 1.40 oz. (39.8 g)

Broken Hill Mine, New South Wales, Australia

This small hand specimen consists of a broken chunck of Microcline, a member of the feldspar group. This piece is in fair to poor condition, showing much breakage, and has crystalline tendencies but no actual crystal form. Some surfaces are flat and apparently cleaved- these have a pearly luster- but others are obviously freshly broken, and have a brighter, vitreous luster. The grass-green color of the material is quite striking, however, as is the fact that it is translucent and contains areas of dim transaprence. There are a few bits of broken, crystalline galena present, and possibly some milky quartz, though it could just be more Microcline with a gray coloration.

Dims: 1.1 x 1.0 x 0.9" (2.8 x 2.5 x 2.3 cm)

Wt: 19.0 g w/ specimen box

Rocket Claim, Teller County, Colorado, U.S.A.

At least 4 Amazonite crystals are intergrown on this specimen. These crystals do not measure more than 0.4" (1.0 cm) along any axis but are in excellent condition, showing very little damage. Their triclinic prismatic form is very good, though there is some slight warping due to intergrowth. All have a pale blue-green coloration and a dull pearly luster. They are accompanied by 3 smoky quartz crystals, only two of which are complete. The piece is glued into a plastic specimen box.

Dims: 2.6 x 2.5 x 1.6" (6.7 x 6.4 x 4.1 cm)

Wt: 4.4 oz. (126 g)

Crystal Peak Mining District, Lake George, Park County, Colorado, U.S.A.

This hand specimen consists of a nearly complete Microcline crystal that is accompanied by 3 smoky quartz crystals. The Microcline has dimensions of 1.8 x 1.3 x 1.2" (4.6 x 3.3 x 3.0 cm) and is in excellent condition, showing almost no fresh damage. Its triclinic prismatic form is very good, though slightly warped due to intergrowth, and it has the standard blue-green color and waxy luster. Bits of several other Microcline crystals are present, but none of these are more than 20% complete. The accompanying smoky quartzes are also in excellent condition and have a somewhat flattened hexagonal prismatic form. Their dark brown color is good, their vitreous luster is rather dull, and they are dimly transparent and mostly cloudy.

Dims: 0.6 x 0.6 x 0.4" (1.6 x 1.6 x 1.0 cm)

Wt: oz. ( g)

Park County, Colorado, U.S.A.

Part of a single, twinned Microcline crystal makes up this small thumbnail specimen. Though it is broken and incomplete, the breakage occurred prior to mining and is slightly healed over. It shows excellent triclinic form, and the twinning, in accordance with the Carlsbad-Law, is excellent and easily visible. It has a creamy, pale brown color and a waxy luster. The crystal is free of any host material and is affixed inside a plastic specimen box with a removable putty.

Dims: 1.5 x 1.4 x 1.2" (3.9 x 3.5 x 3.0 cm)

Wt: 1.0 oz. (28 g)

Crystal Creek, Florissant, Teller County, Colorado, U.S.A.

This hand specimen consists of a single Amazonite (green Microcline) prism that extends from a Perthite ("striped" Microcline) base. This crystal is in good condition, though it looks as if it may have been broken and repaired. If it is repaired, then the repair job is extremely good, as only a heavy crack is evident. The crystal measures 1.3 x 0.9 x 0.5" (3.3 x 2.2 x 1.2 cm) and has a somewhat warped triclinic form that has an odd trait- portions of the green Amazonite crystal seem to fade into the Perthite base with no solid boundary, so that the green color slowly fades and the crystal form slowly becomes massive. Its blue-green color and pearly luster are standard for the specie. A few small, dark smoky quartzes extend sideways from the base of the crystal- one is damaged, but all have excellent form, color and clarity.

Dims: 1.2 x 1.1 x 1.1" (3.0 x 2.8 x 2.7 cm)

Wt: 20 g

Crystal Creek, Florissant, Teller County, Colorado, U.S.A.

Three Amazonite (green Microcline) crystals make up the bulk of this small hand specimen- however, only one of these is complete or undamaged. This crystal is also the largest, and has dimensions of 0.9 x 0.7 x 0.6" (2.2 x 1.9 x 1.5 cm). Its triclinic prismatic form is excellent and its green-blue color and pearly luster are standard for its specie. A few stubby smoky quartz crystals are present, and all seem to extend from a small orthoclase base.

Dims: 2.2 x 2.1 x 1.9" (5.5 x 5.3 x 4.9 cm)

Wt: 2.9 oz. (81 g)

Mount Saint Hilaire, Quebec, Canada

At least 4 intersecting Microcline crystals make up the bulk of this large hand specimen. These crystals are generally worn and incomplete, but all damage appears to have occurred prior to mining. The largest (and seemingly most complete) of the crystals has dimensions of 1.8 x 1.4 x 0.5" (4.5 x 3.5 x 1.3 cm) and a nearly tabular triclinic form that is not very well defined. All have a dull white coloration and a waxy luster at best. They are accompanied by two muscovite books that have an almost rosette form, a cluster of albite blades and what looks like a formation of dark brown, dull "angel-wing" calcite- however, I am not sure exactly what the mineral is.

Dims: 2.1 x 1.9 x 1.7" (5.4 x 4.7 x 4.2 cm)

Wt: 3.4 oz. (97 g)

Bob and Ray Pocket, Crystal Creek, Florissant, Teller County, Colorado, U.S.A.

This hand specimen consists of a single large Microcline crystal that is in very good condition; it shows light damage at its termination but is otherwise intact. Its monoclinic prismatic form is likewise very good, showing obvious twinning. A few zones of white plagioclase are present in the crystal, earning this specimen the name "Perthite". Otherwise, the crystal has the standard blue-green coloration and a pearly-to-waxy luster. It extends from a base made up of albite and another, fractured and incomplete Amazonite.