Initial Statement of Beneficial Ownership (3)

FORM 3	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0104 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person * Mumford Colleen Elizabeth	2. Date of Event Requiring Statement (MM/DD/YYYY) 9/30/2019	3. Issuer Name and Ticker or Trading Symbol CABOT MICROELECTRONICS CORP [CCMP]
(Last)        (First)        (Middle) C/O CABOT MICROELECTRONICS CORPORATION, 870 N COMMONS DRIVE	4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director                          _____ 10% Owner ___X___ Officer (give title below)        _____ Other (specify below) VP, Marketing & Communications /
(Street) AURORA, IL 60504       (City)              (State)              (Zip)	5. If Amendment, Date Original Filed(MM/DD/YYYY)	6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock (1)	1825	D

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security (Instr. 4)	2. Date Exercisable and Expiration Date (MM/DD/YYYY)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Options (Right to Buy)	12/3/2013 (2)	12/3/2022	Common Stock	640	$32.64	D
Stock Options (Right to Buy)	12/3/2014 (3)	12/3/2023	Common Stock	416	$44.10	D
Stock Options (Right to Buy)	12/3/2015 (4)	12/3/2024	Common Stock	363	$46.45	D
Stock Options (Right to Buy)	12/3/2016 (5)	12/3/2025	Common Stock	1324	$42.37	D
Stock Options (Right to Buy)	12/5/2017 (6)	12/5/2026	Common Stock	2740	$60.27	D
Stock Options (Right to Buy)	12/5/2018 (7)	12/5/2027	Common Stock	774	$92.57	D
Stock Options (Right to Buy)	12/6/2019 (8)	12/6/2028	Common Stock	832	$101.73	D

Explanation of Responses:
(1)	Subject to restrictions according to various vesting schedules.
(2)	2012 (FY13) Non-Qualified Stock Option Grant Vesting Schedule: 25% 12/03/2013, 25% 12/03/2014, 25% 12/03/2015, 25% 12/03/2016.
(3)	2013 (FY14) Non-Qualified Stock Option Grant Vesting Schedule: 25% 12/03/2014, 25% 12/03/2015, 25% 12/03/2016, 25% 12/03/2017.
(4)	2014 (FY15) Non-Qualified Stock Option Grant Vesting Schedule: 25% 12/03/2015, 25% 12/03/2016, 25% 12/03/2017, 25% 12/03/2018.
(5)	2015 (FY16) Non-Qualified Stock Option Grant Vesting Schedule: 25% 12/03/2016, 25% 12/03/2017, 25% 12/03/2018, 25% 12/03/2019.
(6)	2016 (FY17) Non-Qualified Stock Option Grant Vesting Schedule: 25% 12/05/2017, 25% 12/05/2018, 25% 12/05/2019, 25% 12/05/2020.
(7)	2017 (FY18) Non-Qualified Stock Option Grant Vesting Schedule: 25% 12/05/2018, 25% 12/05/2019, 25% 12/05/2020, 25% 12/05/2021.
(8)	2018 (FY19) Non-Qualified Stock Option Grant Vesting Schedule: 25% 12/06/2019, 25% 12/06/2020, 25% 12/06/2021, 25% 12/06/2022.

Reporting Owners
Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Mumford Colleen Elizabeth C/O CABOT MICROELECTRONICS CORPORATION 870 N COMMONS DRIVE AURORA, IL 60504			VP, Marketing & Communications

Signatures
/s/ H. Carol Bernstein (Power of Attorney)		10/1/2019
**Signature of Reporting Person		Date