| specifications︰ | Mica Blocks - from OOEE Special size to No 6 size in Clear, Stained 1st, Stained B, HS and DS quality.
Mica Blocks
Mica after extraction from the mines is sorted out and the pieces having area larger than 1" sq. and up and a having a thickness of 7 mils and up are classified separately as Mica Blocks. This mica is the basic raw material for all the various types available for export apart from mica scrap, flakes and powder. These pieces after undergoing size and quality classification as defined in other pages are exported. Mica blocks are irregular in shape.
Mica blocks
The knife dressed sheets of mica with a minimum thickness of each sheet 0.18mm (0.007 inch) is called Mica Blocks. Mica sheets are available in irregular shapes due to natural finishings and are obtained in between the area range of 4.8 sq.cm. to 650 sq. cm. (0.75 sq. inch to 100 & up sq. inch). Average Sheet thickness of each Mica Blocks varies in between 0.18 to 0.40mm (0.007 inch to 0.016 inch)
Normally Mica Blocks Quality are classified in 16 types of specifications as mentioned below :
V-1, Ruby Clear - Hard, of uniform colour, flat, free all stains and foreign inclusions, waves, crackes, buckles and other similar defects. Crystellographic disclouration is permitted to a limited extent.
V-2, Ruby Clear and Slightly Stained - Hard, of uniform colour, fairly flat, free from all vegetable and mineral stains, buckles and other similar defects, and foreign inclusions except for a few tiny air inclusions in not more than one-fourth of the usable area. Crystallographic discolouration permitted to a limited extent.
V-3, Ruby Fair Stained - Hard, of uniform colour, free from all vegetable and mineral stains, cracks, buckles and other similar defects and foreign inclusions, except that may be slightly wavy and may contain slight air inclusions in not more than one-half of the usable area. Crystallographic discolouration is permitted to a limited extent.
V-4, Ruby Gold Stained - Hard, free from vegetable and mineral stains, cracks, buckles and other similar defects, and foreign inclusions, except that may be somewhat wavy but not rippled and may contain medium air inclusions in not more than two-thirds of the usable are, but may not have heavily concentrated air inclusions in any of the usable area. Crystallographic discolouration is permitted.
V-5, Ruby Stained A Quality - Hard, free from cracks and other similar defects and foreign inclusions, except that may be wavy with slight buckles and may contain slight vegetable stains, slight minerals stains not exceeding two specks within the usable area, and the entire area may have air inclusions if not heavily concentrated over more than 1/16 sq. inch for grade 5 and up, and over more than 1/64 sq. inch for grade 5.1/2 and below. Crystallographic discolouration is permitted.
V-6, Ruby A Q - Hard, free from cracks and other similar defects and foreign inclusions, except that may be wavy with slight buckles and may contain medium vegetable stains which are usually brown diffused stains, and the entire area may have air inclusionsif not heavily concentrated. Occasional black dots are allowed. Crystallographic disclouration is permitted.
V-7, Ruby Stained B quality - Hard, free from cracks and other similar defects and foreign inclusions, except that may be wavy and slightly buckled and may contain heavy air inclusions medium vegetable, clay and mineral stains. Crystallographic disclouration is permitted.
V-8, Ruby B Q - Hard, free from cracks and other similar defects and foreign inclusions, except that may be wavy and slightly buckled and may contain heavy air inclusions, heavy vegetable stains and medium mineral stains. Crystallographic discolouration is permitted.
V-9, Ruby Heavy Stained - Hard, free from cracks and other similar defects and foreign inclusions, except that may be wavy and buckled and may contain heavy air inclusions, heavy vegetable stains and medium mineral stains. Crystallographic discolouration is permitted.
V-10, Ruby Densely Stained - May be soft and may contain heavy stains and inclusions, waves, cracks, buckles and other similar defects. Crystallographic discolouration is permitted.
V-11, Black Dotted - Hard, free from cracks and other similar defects, but may contain medium waves, heavy air inclusions, vegetables stains and dispersed black dots. Crystallographic discloration is permitted.
V-12, Black Spotted(or Spotted 1st Quality) - Hard, free from cracks, and other similar defects and foreign inclusions, except that may be medium wavy and may contain slight buckles and vegetables stains, black or red spotted mineral stains, end heavy air inclusions, Crystallographic discloration is permitted.
V-13, Black / Red Stained (or Spotted 2nd Quality) - same as V-12 Quality except that it may be soft and may have black lines and/or short red bars or connected stains.
V-14, Green/Brown First Quality - Flat, hard, of uniform colour free from all vegetables and mineral stains, cracks, buckles, and other similar defects and foreign inclusions, but may contain slight air inclusions in not more than one-half of the usable area.
V-15, Green / Brown 2nd Quality - Hard, free from cracks and other similar defects and foreign inclusions, but may be wavy with slight buckles and may contain medium vegetables stains, and the entire area may have air inclusions if not heavily concentrated Crystallographic discoloration is permitted.
V-16, Green / Brown Stained or BQ - Free from cracks and other similar defects and foreign inclusions, but may be wavy and may contain heavy air inclusions, heavy vegetable stains and medium mineral stains. Crystellographic discoloration is permitted.
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Size Grading
Mica Blocks sizes are graded under accepted International specification of size-grading as appended below :
GRADE DESIGNATION AREA OF USABLE RETANCE MINIMUM DIMENSION OF ONE SIDE OF USABLE RECTANGLE PERMISSIBLE STRIP TOLERANCE
( 1 ) ( 2 ) ( 3 ) ( 4 )
( GRADE / SIZE ) SQ.CM SQ.IN CM IN
OOEE special 645.2 100
& above & above 10.2 4 nil
OEE special 516.1 tlt 645.2 80 tlt 100 10.2 4 nil
Ee special 387.1 tlt 516.1
60 tlt 80 10.2 4 nil
E special 309.7 tlt 387.1
48 tlt 60 10.2 4 nil
Special 232.3 tlt 309.7
36 tlt 48 8.9 3.5 nil
1 154.8 tlt 232.3
24 tlt 36 7.6 3 5% of pieces having width down to end including 5.1cm or ( 2 in)
2 96.8 tlt 154.8
15 tlt 24 5.1 2 5% of pieces having width down to end including 3.8cm or (1.5 in.)
3 64.5 tlt 96.8
10 tlt 15 5.1 2 5% of pieces having width down to end including 3.8cm or (1.5 in.)
4 38.7 tlt 64.5
6 tlt 10 3.8 1.5 5% of pieces having width down to end including 2.5cm or (1 in.)
5 19.4 tlt 38.7 3 tlt 6 2.5 1 nil
5.5 14.5 tlt 19.4 2.25 tlt 3 2.2 7/8 nil
6 6.4 tlt 14.5 1 tlt 2.25 1.9 3 /4 nil
7 4.8 tlt 6.4 0.75 tlt 1 1.6 5/8 nil
(t l t = to less than)
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