Brian, I am working on finding out how mica is graded. I pulled up this document from Uncle Sam. It gives us a few clues.
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[Code of Federal Regulations]
[Title 21, Volume 1, Parts 1 to 99]
[Revised as of April 1, 1996]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR73]
[Page 328-337]
TITLE 21--FOOD AND DRUGS
CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES
PART 73--LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION--Table of Contents
Subpart B--Drugs
Sec. 73.1496 Mica.
(a) Identity. (1) The color additive mica is a white powder obtained
from the naturally occurring mineral, muscovite mica, consisting
predominantly of a potassium aluminum silicate,
K<>2</INF>Al<INF>4</INF>(Al<INF>2</INF>Si<INF>6</INF>O<INF>20</INF>)(O
H)<INF>4</INF> or, alternatively, H<INF>2</INF>KAl<INF>3</INF>
(SiO<INF>4</INF>)<INF>3.</INF> Mica may be identified and
semiquantitatively determined by its characteristic X-ray diffraction
pattern and by its optical properties.
(2) Color additive mixtures for drug use made with mica may contain
only those diluents listed in this subpart as safe and suitable for use
in color additive mixtures for coloring drugs.
(b) Specifications. Mica shall conform to the following
specifications and shall be free from impurities other than those named
to the extent that such other impurities may be avoided by good
manufacturing practice:
Fineness, 100 percent shall pass through a 100-mesh sieve.
Loss on ignition at 600-650 deg.C, not more than 2 percent.
Lead (as Pb), not more than 20 parts per million.
Arsenic (as As), not more than 3 parts per million.
Mercury (as Hg), not more than 1 part per million.
(c) Uses and restrictions. Mica may be safely used in amounts
consistent with good manufacturing practice to color dentifrices and
externally applied drugs, including those for use in the area of the
eye.
(d) Labeling requirements. The label of the color additive and of
any mixture prepared therefrom intended solely or in part for coloring
purposes shall conform to the requirements of Sec. 70.25 of this
chapter.
(e) Exemption from certification. Certification of this color
additive is not necessary for the protection of the public health, and
therefore batches therof are exempt from the certification requirements
of section 721(c) of the act.
[42 FR 38561, July 29, 1977, as amended at 52 FR 29665, Aug. 11, 1987] |
